Call `type_of` for opaque types later in compilation

This ensures that various wf checks have already been done before we
typeck item bodies.

29 files changed, 346 insertions, 417 deletions

diff --git a/src/test/ui/associated-type-bounds/duplicate.rs b/src/test/ui/associated-type-bounds/duplicate.rs
index 6c860530832..39df9ba02fd 100644
--- a/src/test/ui/associated-type-bounds/duplicate.rs
+++ b/src/test/ui/associated-type-bounds/duplicate.rs
@@ -60,11 +60,8 @@ fn FW3<T>() where T: Iterator<Item: 'static, Item: 'static> {}
 //~^ ERROR the value of the associated type `Item` (from trait `Iterator`) is already specified [E0719]
 
 fn FRPIT1() -> impl Iterator<Item: Copy, Item: Send> { iter::empty() }
-//~^ ERROR the value of the associated type `Item` (from trait `Iterator`) is already specified [E0719]
 fn FRPIT2() -> impl Iterator<Item: Copy, Item: Copy> { iter::empty() }
-//~^ ERROR the value of the associated type `Item` (from trait `Iterator`) is already specified [E0719]
 fn FRPIT3() -> impl Iterator<Item: 'static, Item: 'static> { iter::empty() }
-//~^ ERROR the value of the associated type `Item` (from trait `Iterator`) is already specified [E0719]
 fn FAPIT1(_: impl Iterator<Item: Copy, Item: Send>) {}
 //~^ ERROR the value of the associated type `Item` (from trait `Iterator`) is already specified [E0719]
 fn FAPIT2(_: impl Iterator<Item: Copy, Item: Copy>) {}
@@ -107,28 +104,16 @@ type TAW3<T> where T: Iterator<Item: 'static, Item: 'static> = T;
 
 type ETAI1<T: Iterator<Item: Copy, Item: Send>> = impl Copy;
 //~^ ERROR the value of the associated type `Item` (from trait `Iterator`) is already specified [E0719]
-//~| ERROR could not find defining uses
 type ETAI2<T: Iterator<Item: Copy, Item: Copy>> = impl Copy;
 //~^ ERROR the value of the associated type `Item` (from trait `Iterator`) is already specified [E0719]
-//~| ERROR could not find defining uses
 type ETAI3<T: Iterator<Item: 'static, Item: 'static>> = impl Copy;
 //~^ ERROR the value of the associated type `Item` (from trait `Iterator`) is already specified [E0719]
-//~| ERROR could not find defining uses
 type ETAI4 = impl Iterator<Item: Copy, Item: Send>;
 //~^ ERROR the value of the associated type `Item` (from trait `Iterator`) is already specified [E0719]
-//~| ERROR could not find defining uses
-//~| ERROR could not find defining uses
-//~| ERROR could not find defining uses
 type ETAI5 = impl Iterator<Item: Copy, Item: Copy>;
 //~^ ERROR the value of the associated type `Item` (from trait `Iterator`) is already specified [E0719]
-//~| ERROR could not find defining uses
-//~| ERROR could not find defining uses
-//~| ERROR could not find defining uses
 type ETAI6 = impl Iterator<Item: 'static, Item: 'static>;
 //~^ ERROR the value of the associated type `Item` (from trait `Iterator`) is already specified [E0719]
-//~| ERROR could not find defining uses
-//~| ERROR could not find defining uses
-//~| ERROR could not find defining uses
 
 trait TRI1<T: Iterator<Item: Copy, Item: Send>> {}
 //~^ ERROR the value of the associated type `Item` (from trait `Iterator`) is already specified [E0719]
@@ -166,15 +151,9 @@ trait TRA3 { type A: Iterator<Item: 'static, Item: 'static>; }
 
 type TADyn1 = dyn Iterator<Item: Copy, Item: Send>;
 //~^ ERROR the value of the associated type `Item` (from trait `Iterator`) is already specified [E0719]
-//~| ERROR could not find defining uses
-//~| ERROR could not find defining uses
 type TADyn2 = Box<dyn Iterator<Item: Copy, Item: Copy>>;
 //~^ ERROR the value of the associated type `Item` (from trait `Iterator`) is already specified [E0719]
-//~| ERROR could not find defining uses
-//~| ERROR could not find defining uses
 type TADyn3 = dyn Iterator<Item: 'static, Item: 'static>;
 //~^ ERROR the value of the associated type `Item` (from trait `Iterator`) is already specified [E0719]
-//~| ERROR could not find defining uses
-//~| ERROR could not find defining uses
 
 fn main() {}
diff --git a/src/test/ui/associated-type-bounds/duplicate.stderr b/src/test/ui/associated-type-bounds/duplicate.stderr
index ac59e1f2fba..77cd88e524f 100644
--- a/src/test/ui/associated-type-bounds/duplicate.stderr
+++ b/src/test/ui/associated-type-bounds/duplicate.stderr
@@ -200,7 +200,7 @@ LL | fn FW3<T>() where T: Iterator<Item: 'static, Item: 'static> {}
    |                               `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:68:40
+  --> $DIR/duplicate.rs:65:40
    |
 LL | fn FAPIT1(_: impl Iterator<Item: Copy, Item: Send>) {}
    |                            ----------  ^^^^^^^^^^ re-bound here
@@ -208,7 +208,7 @@ LL | fn FAPIT1(_: impl Iterator<Item: Copy, Item: Send>) {}
    |                            `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:70:40
+  --> $DIR/duplicate.rs:67:40
    |
 LL | fn FAPIT2(_: impl Iterator<Item: Copy, Item: Copy>) {}
    |                            ----------  ^^^^^^^^^^ re-bound here
@@ -216,7 +216,7 @@ LL | fn FAPIT2(_: impl Iterator<Item: Copy, Item: Copy>) {}
    |                            `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:72:43
+  --> $DIR/duplicate.rs:69:43
    |
 LL | fn FAPIT3(_: impl Iterator<Item: 'static, Item: 'static>) {}
    |                            -------------  ^^^^^^^^^^^^^ re-bound here
@@ -224,7 +224,7 @@ LL | fn FAPIT3(_: impl Iterator<Item: 'static, Item: 'static>) {}
    |                            `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:75:39
+  --> $DIR/duplicate.rs:72:39
    |
 LL | const CIT1: impl Iterator<Item: Copy, Item: Send> = iter::empty();
    |                           ----------  ^^^^^^^^^^ re-bound here
@@ -232,7 +232,7 @@ LL | const CIT1: impl Iterator<Item: Copy, Item: Send> = iter::empty();
    |                           `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:77:39
+  --> $DIR/duplicate.rs:74:39
    |
 LL | const CIT2: impl Iterator<Item: Copy, Item: Copy> = iter::empty();
    |                           ----------  ^^^^^^^^^^ re-bound here
@@ -240,7 +240,7 @@ LL | const CIT2: impl Iterator<Item: Copy, Item: Copy> = iter::empty();
    |                           `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:79:42
+  --> $DIR/duplicate.rs:76:42
    |
 LL | const CIT3: impl Iterator<Item: 'static, Item: 'static> = iter::empty();
    |                           -------------  ^^^^^^^^^^^^^ re-bound here
@@ -248,7 +248,7 @@ LL | const CIT3: impl Iterator<Item: 'static, Item: 'static> = iter::empty();
    |                           `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:81:40
+  --> $DIR/duplicate.rs:78:40
    |
 LL | static SIT1: impl Iterator<Item: Copy, Item: Send> = iter::empty();
    |                            ----------  ^^^^^^^^^^ re-bound here
@@ -256,7 +256,7 @@ LL | static SIT1: impl Iterator<Item: Copy, Item: Send> = iter::empty();
    |                            `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:83:40
+  --> $DIR/duplicate.rs:80:40
    |
 LL | static SIT2: impl Iterator<Item: Copy, Item: Copy> = iter::empty();
    |                            ----------  ^^^^^^^^^^ re-bound here
@@ -264,7 +264,7 @@ LL | static SIT2: impl Iterator<Item: Copy, Item: Copy> = iter::empty();
    |                            `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:85:43
+  --> $DIR/duplicate.rs:82:43
    |
 LL | static SIT3: impl Iterator<Item: 'static, Item: 'static> = iter::empty();
    |                            -------------  ^^^^^^^^^^^^^ re-bound here
@@ -272,7 +272,7 @@ LL | static SIT3: impl Iterator<Item: 'static, Item: 'static> = iter::empty();
    |                            `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:88:46
+  --> $DIR/duplicate.rs:85:46
    |
 LL | fn lit1() { let _: impl Iterator<Item: Copy, Item: Send> = iter::empty(); }
    |                                  ----------  ^^^^^^^^^^ re-bound here
@@ -280,7 +280,7 @@ LL | fn lit1() { let _: impl Iterator<Item: Copy, Item: Send> = iter::empty(); }
    |                                  `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:90:46
+  --> $DIR/duplicate.rs:87:46
    |
 LL | fn lit2() { let _: impl Iterator<Item: Copy, Item: Copy> = iter::empty(); }
    |                                  ----------  ^^^^^^^^^^ re-bound here
@@ -288,7 +288,7 @@ LL | fn lit2() { let _: impl Iterator<Item: Copy, Item: Copy> = iter::empty(); }
    |                                  `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:92:49
+  --> $DIR/duplicate.rs:89:49
    |
 LL | fn lit3() { let _: impl Iterator<Item: 'static, Item: 'static> = iter::empty(); }
    |                                  -------------  ^^^^^^^^^^^^^ re-bound here
@@ -296,7 +296,7 @@ LL | fn lit3() { let _: impl Iterator<Item: 'static, Item: 'static> = iter::empt
    |                                  `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:95:35
+  --> $DIR/duplicate.rs:92:35
    |
 LL | type TAI1<T: Iterator<Item: Copy, Item: Send>> = T;
    |                       ----------  ^^^^^^^^^^ re-bound here
@@ -304,7 +304,7 @@ LL | type TAI1<T: Iterator<Item: Copy, Item: Send>> = T;
    |                       `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:97:35
+  --> $DIR/duplicate.rs:94:35
    |
 LL | type TAI2<T: Iterator<Item: Copy, Item: Copy>> = T;
    |                       ----------  ^^^^^^^^^^ re-bound here
@@ -312,7 +312,7 @@ LL | type TAI2<T: Iterator<Item: Copy, Item: Copy>> = T;
    |                       `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:99:38
+  --> $DIR/duplicate.rs:96:38
    |
 LL | type TAI3<T: Iterator<Item: 'static, Item: 'static>> = T;
    |                       -------------  ^^^^^^^^^^^^^ re-bound here
@@ -320,7 +320,7 @@ LL | type TAI3<T: Iterator<Item: 'static, Item: 'static>> = T;
    |                       `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:101:44
+  --> $DIR/duplicate.rs:98:44
    |
 LL | type TAW1<T> where T: Iterator<Item: Copy, Item: Send> = T;
    |                                ----------  ^^^^^^^^^^ re-bound here
@@ -328,7 +328,7 @@ LL | type TAW1<T> where T: Iterator<Item: Copy, Item: Send> = T;
    |                                `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:103:44
+  --> $DIR/duplicate.rs:100:44
    |
 LL | type TAW2<T> where T: Iterator<Item: Copy, Item: Copy> = T;
    |                                ----------  ^^^^^^^^^^ re-bound here
@@ -336,7 +336,7 @@ LL | type TAW2<T> where T: Iterator<Item: Copy, Item: Copy> = T;
    |                                `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:105:47
+  --> $DIR/duplicate.rs:102:47
    |
 LL | type TAW3<T> where T: Iterator<Item: 'static, Item: 'static> = T;
    |                                -------------  ^^^^^^^^^^^^^ re-bound here
@@ -344,7 +344,7 @@ LL | type TAW3<T> where T: Iterator<Item: 'static, Item: 'static> = T;
    |                                `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:108:36
+  --> $DIR/duplicate.rs:105:36
    |
 LL | type ETAI1<T: Iterator<Item: Copy, Item: Send>> = impl Copy;
    |                        ----------  ^^^^^^^^^^ re-bound here
@@ -352,99 +352,39 @@ LL | type ETAI1<T: Iterator<Item: Copy, Item: Send>> = impl Copy;
    |                        `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:62:42
-   |
-LL | fn FRPIT1() -> impl Iterator<Item: Copy, Item: Send> { iter::empty() }
-   |                              ----------  ^^^^^^^^^^ re-bound here
-   |                              |
-   |                              `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:64:42
-   |
-LL | fn FRPIT2() -> impl Iterator<Item: Copy, Item: Copy> { iter::empty() }
-   |                              ----------  ^^^^^^^^^^ re-bound here
-   |                              |
-   |                              `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:66:45
-   |
-LL | fn FRPIT3() -> impl Iterator<Item: 'static, Item: 'static> { iter::empty() }
-   |                              -------------  ^^^^^^^^^^^^^ re-bound here
-   |                              |
-   |                              `Item` bound here first
-
-error: could not find defining uses
-  --> $DIR/duplicate.rs:108:51
-   |
-LL | type ETAI1<T: Iterator<Item: Copy, Item: Send>> = impl Copy;
-   |                                                   ^^^^^^^^^
-
-error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:111:36
+  --> $DIR/duplicate.rs:107:36
    |
 LL | type ETAI2<T: Iterator<Item: Copy, Item: Copy>> = impl Copy;
    |                        ----------  ^^^^^^^^^^ re-bound here
    |                        |
    |                        `Item` bound here first
 
-error: could not find defining uses
-  --> $DIR/duplicate.rs:111:51
-   |
-LL | type ETAI2<T: Iterator<Item: Copy, Item: Copy>> = impl Copy;
-   |                                                   ^^^^^^^^^
-
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:114:39
+  --> $DIR/duplicate.rs:109:39
    |
 LL | type ETAI3<T: Iterator<Item: 'static, Item: 'static>> = impl Copy;
    |                        -------------  ^^^^^^^^^^^^^ re-bound here
    |                        |
    |                        `Item` bound here first
 
-error: could not find defining uses
-  --> $DIR/duplicate.rs:114:57
-   |
-LL | type ETAI3<T: Iterator<Item: 'static, Item: 'static>> = impl Copy;
-   |                                                         ^^^^^^^^^
-
-error: could not find defining uses
-  --> $DIR/duplicate.rs:117:14
-   |
-LL | type ETAI4 = impl Iterator<Item: Copy, Item: Send>;
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:117:40
+  --> $DIR/duplicate.rs:111:40
    |
 LL | type ETAI4 = impl Iterator<Item: Copy, Item: Send>;
    |                            ----------  ^^^^^^^^^^ re-bound here
    |                            |
    |                            `Item` bound here first
 
-error: could not find defining uses
-  --> $DIR/duplicate.rs:122:14
-   |
-LL | type ETAI5 = impl Iterator<Item: Copy, Item: Copy>;
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:122:40
+  --> $DIR/duplicate.rs:113:40
    |
 LL | type ETAI5 = impl Iterator<Item: Copy, Item: Copy>;
    |                            ----------  ^^^^^^^^^^ re-bound here
    |                            |
    |                            `Item` bound here first
 
-error: could not find defining uses
-  --> $DIR/duplicate.rs:127:14
-   |
-LL | type ETAI6 = impl Iterator<Item: 'static, Item: 'static>;
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:127:43
+  --> $DIR/duplicate.rs:115:43
    |
 LL | type ETAI6 = impl Iterator<Item: 'static, Item: 'static>;
    |                            -------------  ^^^^^^^^^^^^^ re-bound here
@@ -452,7 +392,7 @@ LL | type ETAI6 = impl Iterator<Item: 'static, Item: 'static>;
    |                            `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:133:36
+  --> $DIR/duplicate.rs:118:36
    |
 LL | trait TRI1<T: Iterator<Item: Copy, Item: Send>> {}
    |                        ----------  ^^^^^^^^^^ re-bound here
@@ -460,7 +400,7 @@ LL | trait TRI1<T: Iterator<Item: Copy, Item: Send>> {}
    |                        `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:135:36
+  --> $DIR/duplicate.rs:120:36
    |
 LL | trait TRI2<T: Iterator<Item: Copy, Item: Copy>> {}
    |                        ----------  ^^^^^^^^^^ re-bound here
@@ -468,7 +408,7 @@ LL | trait TRI2<T: Iterator<Item: Copy, Item: Copy>> {}
    |                        `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:137:39
+  --> $DIR/duplicate.rs:122:39
    |
 LL | trait TRI3<T: Iterator<Item: 'static, Item: 'static>> {}
    |                        -------------  ^^^^^^^^^^^^^ re-bound here
@@ -476,7 +416,7 @@ LL | trait TRI3<T: Iterator<Item: 'static, Item: 'static>> {}
    |                        `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:139:34
+  --> $DIR/duplicate.rs:124:34
    |
 LL | trait TRS1: Iterator<Item: Copy, Item: Send> {}
    |                      ----------  ^^^^^^^^^^ re-bound here
@@ -484,7 +424,7 @@ LL | trait TRS1: Iterator<Item: Copy, Item: Send> {}
    |                      `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:141:34
+  --> $DIR/duplicate.rs:126:34
    |
 LL | trait TRS2: Iterator<Item: Copy, Item: Copy> {}
    |                      ----------  ^^^^^^^^^^ re-bound here
@@ -492,7 +432,7 @@ LL | trait TRS2: Iterator<Item: Copy, Item: Copy> {}
    |                      `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:143:37
+  --> $DIR/duplicate.rs:128:37
    |
 LL | trait TRS3: Iterator<Item: 'static, Item: 'static> {}
    |                      -------------  ^^^^^^^^^^^^^ re-bound here
@@ -500,7 +440,7 @@ LL | trait TRS3: Iterator<Item: 'static, Item: 'static> {}
    |                      `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:145:45
+  --> $DIR/duplicate.rs:130:45
    |
 LL | trait TRW1<T> where T: Iterator<Item: Copy, Item: Send> {}
    |                                 ----------  ^^^^^^^^^^ re-bound here
@@ -508,7 +448,7 @@ LL | trait TRW1<T> where T: Iterator<Item: Copy, Item: Send> {}
    |                                 `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:147:45
+  --> $DIR/duplicate.rs:132:45
    |
 LL | trait TRW2<T> where T: Iterator<Item: Copy, Item: Copy> {}
    |                                 ----------  ^^^^^^^^^^ re-bound here
@@ -516,7 +456,7 @@ LL | trait TRW2<T> where T: Iterator<Item: Copy, Item: Copy> {}
    |                                 `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:149:48
+  --> $DIR/duplicate.rs:134:48
    |
 LL | trait TRW3<T> where T: Iterator<Item: 'static, Item: 'static> {}
    |                                 -------------  ^^^^^^^^^^^^^ re-bound here
@@ -524,7 +464,7 @@ LL | trait TRW3<T> where T: Iterator<Item: 'static, Item: 'static> {}
    |                                 `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:151:46
+  --> $DIR/duplicate.rs:136:46
    |
 LL | trait TRSW1 where Self: Iterator<Item: Copy, Item: Send> {}
    |                                  ----------  ^^^^^^^^^^ re-bound here
@@ -532,7 +472,7 @@ LL | trait TRSW1 where Self: Iterator<Item: Copy, Item: Send> {}
    |                                  `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:151:46
+  --> $DIR/duplicate.rs:136:46
    |
 LL | trait TRSW1 where Self: Iterator<Item: Copy, Item: Send> {}
    |                                  ----------  ^^^^^^^^^^ re-bound here
@@ -540,7 +480,7 @@ LL | trait TRSW1 where Self: Iterator<Item: Copy, Item: Send> {}
    |                                  `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:154:46
+  --> $DIR/duplicate.rs:139:46
    |
 LL | trait TRSW2 where Self: Iterator<Item: Copy, Item: Copy> {}
    |                                  ----------  ^^^^^^^^^^ re-bound here
@@ -548,7 +488,7 @@ LL | trait TRSW2 where Self: Iterator<Item: Copy, Item: Copy> {}
    |                                  `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:154:46
+  --> $DIR/duplicate.rs:139:46
    |
 LL | trait TRSW2 where Self: Iterator<Item: Copy, Item: Copy> {}
    |                                  ----------  ^^^^^^^^^^ re-bound here
@@ -556,7 +496,7 @@ LL | trait TRSW2 where Self: Iterator<Item: Copy, Item: Copy> {}
    |                                  `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:157:49
+  --> $DIR/duplicate.rs:142:49
    |
 LL | trait TRSW3 where Self: Iterator<Item: 'static, Item: 'static> {}
    |                                  -------------  ^^^^^^^^^^^^^ re-bound here
@@ -564,7 +504,7 @@ LL | trait TRSW3 where Self: Iterator<Item: 'static, Item: 'static> {}
    |                                  `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:157:49
+  --> $DIR/duplicate.rs:142:49
    |
 LL | trait TRSW3 where Self: Iterator<Item: 'static, Item: 'static> {}
    |                                  -------------  ^^^^^^^^^^^^^ re-bound here
@@ -572,7 +512,7 @@ LL | trait TRSW3 where Self: Iterator<Item: 'static, Item: 'static> {}
    |                                  `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:160:43
+  --> $DIR/duplicate.rs:145:43
    |
 LL | trait TRA1 { type A: Iterator<Item: Copy, Item: Send>; }
    |                               ----------  ^^^^^^^^^^ re-bound here
@@ -580,7 +520,7 @@ LL | trait TRA1 { type A: Iterator<Item: Copy, Item: Send>; }
    |                               `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:162:43
+  --> $DIR/duplicate.rs:147:43
    |
 LL | trait TRA2 { type A: Iterator<Item: Copy, Item: Copy>; }
    |                               ----------  ^^^^^^^^^^ re-bound here
@@ -588,7 +528,7 @@ LL | trait TRA2 { type A: Iterator<Item: Copy, Item: Copy>; }
    |                               `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:164:46
+  --> $DIR/duplicate.rs:149:46
    |
 LL | trait TRA3 { type A: Iterator<Item: 'static, Item: 'static>; }
    |                               -------------  ^^^^^^^^^^^^^ re-bound here
@@ -596,7 +536,7 @@ LL | trait TRA3 { type A: Iterator<Item: 'static, Item: 'static>; }
    |                               `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:167:40
+  --> $DIR/duplicate.rs:152:40
    |
 LL | type TADyn1 = dyn Iterator<Item: Copy, Item: Send>;
    |                            ----------  ^^^^^^^^^^ re-bound here
@@ -604,7 +544,7 @@ LL | type TADyn1 = dyn Iterator<Item: Copy, Item: Send>;
    |                            `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:171:44
+  --> $DIR/duplicate.rs:154:44
    |
 LL | type TADyn2 = Box<dyn Iterator<Item: Copy, Item: Copy>>;
    |                                ----------  ^^^^^^^^^^ re-bound here
@@ -612,85 +552,13 @@ LL | type TADyn2 = Box<dyn Iterator<Item: Copy, Item: Copy>>;
    |                                `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
-  --> $DIR/duplicate.rs:175:43
+  --> $DIR/duplicate.rs:156:43
    |
 LL | type TADyn3 = dyn Iterator<Item: 'static, Item: 'static>;
    |                            -------------  ^^^^^^^^^^^^^ re-bound here
    |                            |
    |                            `Item` bound here first
 
-error: could not find defining uses
-  --> $DIR/duplicate.rs:117:28
-   |
-LL | type ETAI4 = impl Iterator<Item: Copy, Item: Send>;
-   |                            ^^^^^^^^^^
-
-error: could not find defining uses
-  --> $DIR/duplicate.rs:117:40
-   |
-LL | type ETAI4 = impl Iterator<Item: Copy, Item: Send>;
-   |                                        ^^^^^^^^^^
-
-error: could not find defining uses
-  --> $DIR/duplicate.rs:122:28
-   |
-LL | type ETAI5 = impl Iterator<Item: Copy, Item: Copy>;
-   |                            ^^^^^^^^^^
-
-error: could not find defining uses
-  --> $DIR/duplicate.rs:122:40
-   |
-LL | type ETAI5 = impl Iterator<Item: Copy, Item: Copy>;
-   |                                        ^^^^^^^^^^
-
-error: could not find defining uses
-  --> $DIR/duplicate.rs:127:28
-   |
-LL | type ETAI6 = impl Iterator<Item: 'static, Item: 'static>;
-   |                            ^^^^^^^^^^^^^
-
-error: could not find defining uses
-  --> $DIR/duplicate.rs:127:43
-   |
-LL | type ETAI6 = impl Iterator<Item: 'static, Item: 'static>;
-   |                                           ^^^^^^^^^^^^^
-
-error: could not find defining uses
-  --> $DIR/duplicate.rs:167:28
-   |
-LL | type TADyn1 = dyn Iterator<Item: Copy, Item: Send>;
-   |                            ^^^^^^^^^^
-
-error: could not find defining uses
-  --> $DIR/duplicate.rs:167:40
-   |
-LL | type TADyn1 = dyn Iterator<Item: Copy, Item: Send>;
-   |                                        ^^^^^^^^^^
-
-error: could not find defining uses
-  --> $DIR/duplicate.rs:171:32
-   |
-LL | type TADyn2 = Box<dyn Iterator<Item: Copy, Item: Copy>>;
-   |                                ^^^^^^^^^^
-
-error: could not find defining uses
-  --> $DIR/duplicate.rs:171:44
-   |
-LL | type TADyn2 = Box<dyn Iterator<Item: Copy, Item: Copy>>;
-   |                                            ^^^^^^^^^^
-
-error: could not find defining uses
-  --> $DIR/duplicate.rs:175:28
-   |
-LL | type TADyn3 = dyn Iterator<Item: 'static, Item: 'static>;
-   |                            ^^^^^^^^^^^^^
-
-error: could not find defining uses
-  --> $DIR/duplicate.rs:175:43
-   |
-LL | type TADyn3 = dyn Iterator<Item: 'static, Item: 'static>;
-   |                                           ^^^^^^^^^^^^^
-
-error: aborting due to 90 previous errors; 1 warning emitted
+error: aborting due to 69 previous errors; 1 warning emitted
 
 For more information about this error, try `rustc --explain E0719`.
diff --git a/src/test/ui/associated-type-bounds/inside-adt.rs b/src/test/ui/associated-type-bounds/inside-adt.rs
index b74c03829b4..5af05738750 100644
--- a/src/test/ui/associated-type-bounds/inside-adt.rs
+++ b/src/test/ui/associated-type-bounds/inside-adt.rs
@@ -3,32 +3,27 @@
 
 struct S1 { f: dyn Iterator<Item: Copy> }
 //~^ ERROR associated type bounds are not allowed within structs, enums, or unions
-//~| ERROR could not find defining uses
 struct S2 { f: Box<dyn Iterator<Item: Copy>> }
 //~^ ERROR associated type bounds are not allowed within structs, enums, or unions
-//~| ERROR could not find defining uses
 struct S3 { f: dyn Iterator<Item: 'static> }
 //~^ ERROR associated type bounds are not allowed within structs, enums, or unions
-//~| ERROR could not find defining uses
 
 enum E1 { V(dyn Iterator<Item: Copy>) }
 //~^ ERROR associated type bounds are not allowed within structs, enums, or unions
-//~| ERROR could not find defining uses
+//~| ERROR the size for values of type `(dyn Iterator<Item = impl Copy> + 'static)`
 enum E2 { V(Box<dyn Iterator<Item: Copy>>) }
 //~^ ERROR associated type bounds are not allowed within structs, enums, or unions
-//~| ERROR could not find defining uses
 enum E3 { V(dyn Iterator<Item: 'static>) }
 //~^ ERROR associated type bounds are not allowed within structs, enums, or unions
-//~| ERROR could not find defining uses
+//~| ERROR the size for values of type `(dyn Iterator<Item = impl Sized> + 'static)`
 
 union U1 { f: dyn Iterator<Item: Copy> }
 //~^ ERROR associated type bounds are not allowed within structs, enums, or unions
-//~| ERROR could not find defining uses
+//~| ERROR the size for values of type `(dyn Iterator<Item = impl Copy> + 'static)`
 union U2 { f: Box<dyn Iterator<Item: Copy>> }
 //~^ ERROR associated type bounds are not allowed within structs, enums, or unions
-//~| ERROR could not find defining uses
 union U3 { f: dyn Iterator<Item: 'static> }
 //~^ ERROR associated type bounds are not allowed within structs, enums, or unions
-//~| ERROR could not find defining uses
+//~| ERROR the size for values of type `(dyn Iterator<Item = impl Sized> + 'static)`
 
 fn main() {}
diff --git a/src/test/ui/associated-type-bounds/inside-adt.stderr b/src/test/ui/associated-type-bounds/inside-adt.stderr
index a532bb0c766..74e858ca861 100644
--- a/src/test/ui/associated-type-bounds/inside-adt.stderr
+++ b/src/test/ui/associated-type-bounds/inside-adt.stderr
@@ -5,106 +5,125 @@ LL | struct S1 { f: dyn Iterator<Item: Copy> }
    |                             ^^^^^^^^^^
 
 error: associated type bounds are not allowed within structs, enums, or unions
-  --> $DIR/inside-adt.rs:7:33
+  --> $DIR/inside-adt.rs:6:33
    |
 LL | struct S2 { f: Box<dyn Iterator<Item: Copy>> }
    |                                 ^^^^^^^^^^
 
 error: associated type bounds are not allowed within structs, enums, or unions
-  --> $DIR/inside-adt.rs:10:29
+  --> $DIR/inside-adt.rs:8:29
    |
 LL | struct S3 { f: dyn Iterator<Item: 'static> }
    |                             ^^^^^^^^^^^^^
 
 error: associated type bounds are not allowed within structs, enums, or unions
-  --> $DIR/inside-adt.rs:14:26
+  --> $DIR/inside-adt.rs:11:26
    |
 LL | enum E1 { V(dyn Iterator<Item: Copy>) }
    |                          ^^^^^^^^^^
 
 error: associated type bounds are not allowed within structs, enums, or unions
-  --> $DIR/inside-adt.rs:17:30
+  --> $DIR/inside-adt.rs:14:30
    |
 LL | enum E2 { V(Box<dyn Iterator<Item: Copy>>) }
    |                              ^^^^^^^^^^
 
 error: associated type bounds are not allowed within structs, enums, or unions
-  --> $DIR/inside-adt.rs:20:26
+  --> $DIR/inside-adt.rs:16:26
    |
 LL | enum E3 { V(dyn Iterator<Item: 'static>) }
    |                          ^^^^^^^^^^^^^
 
 error: associated type bounds are not allowed within structs, enums, or unions
-  --> $DIR/inside-adt.rs:24:28
+  --> $DIR/inside-adt.rs:20:28
    |
 LL | union U1 { f: dyn Iterator<Item: Copy> }
    |                            ^^^^^^^^^^
 
 error: associated type bounds are not allowed within structs, enums, or unions
-  --> $DIR/inside-adt.rs:27:32
+  --> $DIR/inside-adt.rs:23:32
    |
 LL | union U2 { f: Box<dyn Iterator<Item: Copy>> }
    |                                ^^^^^^^^^^
 
 error: associated type bounds are not allowed within structs, enums, or unions
-  --> $DIR/inside-adt.rs:30:28
+  --> $DIR/inside-adt.rs:25:28
    |
 LL | union U3 { f: dyn Iterator<Item: 'static> }
    |                            ^^^^^^^^^^^^^
 
-error: could not find defining uses
-  --> $DIR/inside-adt.rs:4:29
+error[E0277]: the size for values of type `(dyn Iterator<Item = impl Copy> + 'static)` cannot be known at compilation time
+  --> $DIR/inside-adt.rs:11:13
    |
-LL | struct S1 { f: dyn Iterator<Item: Copy> }
-   |                             ^^^^^^^^^^
-
-error: could not find defining uses
-  --> $DIR/inside-adt.rs:7:33
+LL | enum E1 { V(dyn Iterator<Item: Copy>) }
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
    |
-LL | struct S2 { f: Box<dyn Iterator<Item: Copy>> }
-   |                                 ^^^^^^^^^^
-
-error: could not find defining uses
-  --> $DIR/inside-adt.rs:10:29
+   = help: the trait `Sized` is not implemented for `(dyn Iterator<Item = impl Copy> + 'static)`
+   = note: no field of an enum variant may have a dynamically sized type
+   = help: change the field's type to have a statically known size
+help: borrowed types always have a statically known size
    |
-LL | struct S3 { f: dyn Iterator<Item: 'static> }
-   |                             ^^^^^^^^^^^^^
-
-error: could not find defining uses
-  --> $DIR/inside-adt.rs:14:26
+LL | enum E1 { V(&dyn Iterator<Item: Copy>) }
+   |             ^
+help: the `Box` type always has a statically known size and allocates its contents in the heap
    |
-LL | enum E1 { V(dyn Iterator<Item: Copy>) }
-   |                          ^^^^^^^^^^
+LL | enum E1 { V(Box<dyn Iterator<Item: Copy>>) }
+   |             ^^^^                        ^
 
-error: could not find defining uses
-  --> $DIR/inside-adt.rs:17:30
-   |
-LL | enum E2 { V(Box<dyn Iterator<Item: Copy>>) }
-   |                              ^^^^^^^^^^
-
-error: could not find defining uses
-  --> $DIR/inside-adt.rs:20:26
+error[E0277]: the size for values of type `(dyn Iterator<Item = impl Sized> + 'static)` cannot be known at compilation time
+  --> $DIR/inside-adt.rs:16:13
    |
 LL | enum E3 { V(dyn Iterator<Item: 'static>) }
-   |                          ^^^^^^^^^^^^^
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `(dyn Iterator<Item = impl Sized> + 'static)`
+   = note: no field of an enum variant may have a dynamically sized type
+   = help: change the field's type to have a statically known size
+help: borrowed types always have a statically known size
+   |
+LL | enum E3 { V(&dyn Iterator<Item: 'static>) }
+   |             ^
+help: the `Box` type always has a statically known size and allocates its contents in the heap
+   |
+LL | enum E3 { V(Box<dyn Iterator<Item: 'static>>) }
+   |             ^^^^                           ^
 
-error: could not find defining uses
-  --> $DIR/inside-adt.rs:24:28
+error[E0277]: the size for values of type `(dyn Iterator<Item = impl Copy> + 'static)` cannot be known at compilation time
+  --> $DIR/inside-adt.rs:20:15
    |
 LL | union U1 { f: dyn Iterator<Item: Copy> }
-   |                            ^^^^^^^^^^
-
-error: could not find defining uses
-  --> $DIR/inside-adt.rs:27:32
+   |               ^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
    |
-LL | union U2 { f: Box<dyn Iterator<Item: Copy>> }
-   |                                ^^^^^^^^^^
+   = help: the trait `Sized` is not implemented for `(dyn Iterator<Item = impl Copy> + 'static)`
+   = note: no field of a union may have a dynamically sized type
+   = help: change the field's type to have a statically known size
+help: borrowed types always have a statically known size
+   |
+LL | union U1 { f: &dyn Iterator<Item: Copy> }
+   |               ^
+help: the `Box` type always has a statically known size and allocates its contents in the heap
+   |
+LL | union U1 { f: Box<dyn Iterator<Item: Copy>> }
+   |               ^^^^                        ^
 
-error: could not find defining uses
-  --> $DIR/inside-adt.rs:30:28
+error[E0277]: the size for values of type `(dyn Iterator<Item = impl Sized> + 'static)` cannot be known at compilation time
+  --> $DIR/inside-adt.rs:25:15
    |
 LL | union U3 { f: dyn Iterator<Item: 'static> }
-   |                            ^^^^^^^^^^^^^
+   |               ^^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `(dyn Iterator<Item = impl Sized> + 'static)`
+   = note: no field of a union may have a dynamically sized type
+   = help: change the field's type to have a statically known size
+help: borrowed types always have a statically known size
+   |
+LL | union U3 { f: &dyn Iterator<Item: 'static> }
+   |               ^
+help: the `Box` type always has a statically known size and allocates its contents in the heap
+   |
+LL | union U3 { f: Box<dyn Iterator<Item: 'static>> }
+   |               ^^^^                           ^
 
-error: aborting due to 18 previous errors
+error: aborting due to 13 previous errors
 
+For more information about this error, try `rustc --explain E0277`.
diff --git a/src/test/ui/async-await/issues/issue-65159.rs b/src/test/ui/async-await/issues/issue-65159.rs
index 2f80435046b..4f160fccc01 100644
--- a/src/test/ui/async-await/issues/issue-65159.rs
+++ b/src/test/ui/async-await/issues/issue-65159.rs
@@ -5,7 +5,7 @@
 async fn copy() -> Result<()> //~ ERROR wrong number of type arguments
 {
     Ok(())
-    //~^ type annotations needed
+    //~^ ERROR type annotations needed
 }
 
 fn main() { }
diff --git a/src/test/ui/impl-trait/issue-55872-1.rs b/src/test/ui/impl-trait/issue-55872-1.rs
index 99ac4617b41..a746ed09af5 100644
--- a/src/test/ui/impl-trait/issue-55872-1.rs
+++ b/src/test/ui/impl-trait/issue-55872-1.rs
@@ -1,8 +1,7 @@
 // ignore-tidy-linelength
 #![feature(type_alias_impl_trait)]
 
-pub trait Bar
-{
+pub trait Bar {
     type E: Copy;
 
     fn foo<T>() -> Self::E;
@@ -14,7 +13,8 @@ impl<S: Default> Bar for S {
     //~^^ ERROR the trait bound `T: Copy` is not satisfied in `(S, T)` [E0277]
 
     fn foo<T: Default>() -> Self::E {
-    //~^ ERROR type parameter `T` is part of concrete type but not used in parameter list for the `impl Trait` type alias
+        //~^ ERROR type parameter `T` is part of concrete type but not used in parameter list for the `impl Trait` type alias
+        //~| ERROR impl has stricter requirements than trait
         (S::default(), T::default())
     }
 }
diff --git a/src/test/ui/impl-trait/issue-55872-1.stderr b/src/test/ui/impl-trait/issue-55872-1.stderr
index a9f73947853..db49d988bb8 100644
--- a/src/test/ui/impl-trait/issue-55872-1.stderr
+++ b/src/test/ui/impl-trait/issue-55872-1.stderr
@@ -1,5 +1,14 @@
+error[E0276]: impl has stricter requirements than trait
+  --> $DIR/issue-55872-1.rs:15:5
+   |
+LL |     fn foo<T>() -> Self::E;
+   |     ----------------------- definition of `foo` from trait
+...
+LL |     fn foo<T: Default>() -> Self::E {
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl has extra requirement `T: Default`
+
 error[E0277]: the trait bound `S: Copy` is not satisfied in `(S, T)`
-  --> $DIR/issue-55872-1.rs:12:14
+  --> $DIR/issue-55872-1.rs:11:14
    |
 LL |     type E = impl Copy;
    |              ^^^^^^^^^ within `(S, T)`, the trait `Copy` is not implemented for `S`
@@ -12,7 +21,7 @@ LL | impl<S: Default + Copy> Bar for S {
    |                 ^^^^^^
 
 error[E0277]: the trait bound `T: Copy` is not satisfied in `(S, T)`
-  --> $DIR/issue-55872-1.rs:12:14
+  --> $DIR/issue-55872-1.rs:11:14
    |
 LL |     type E = impl Copy;
    |              ^^^^^^^^^ within `(S, T)`, the trait `Copy` is not implemented for `T`
@@ -25,15 +34,17 @@ LL |     fn foo<T: Default + Copy>() -> Self::E {
    |                       ^^^^^^
 
 error: type parameter `T` is part of concrete type but not used in parameter list for the `impl Trait` type alias
-  --> $DIR/issue-55872-1.rs:16:37
+  --> $DIR/issue-55872-1.rs:15:37
    |
 LL |       fn foo<T: Default>() -> Self::E {
    |  _____________________________________^
 LL | |
+LL | |
 LL | |         (S::default(), T::default())
 LL | |     }
    | |_____^
 
-error: aborting due to 3 previous errors
+error: aborting due to 4 previous errors
 
-For more information about this error, try `rustc --explain E0277`.
+Some errors have detailed explanations: E0276, E0277.
+For more information about an error, try `rustc --explain E0276`.
diff --git a/src/test/ui/impl-trait/where-allowed.rs b/src/test/ui/impl-trait/where-allowed.rs
index 211a14ed4dd..72b880fb92c 100644
--- a/src/test/ui/impl-trait/where-allowed.rs
+++ b/src/test/ui/impl-trait/where-allowed.rs
@@ -56,10 +56,12 @@ fn in_impl_Fn_return_in_parameters(_: &impl Fn() -> impl Debug) { panic!() }
 fn in_impl_Fn_parameter_in_return() -> &'static impl Fn(impl Debug) { panic!() }
 //~^ ERROR `impl Trait` not allowed outside of function and inherent method return types
 //~| ERROR nested `impl Trait` is not allowed
+//~| ERROR cannot resolve opaque type
 
 // Disallowed
 fn in_impl_Fn_return_in_return() -> &'static impl Fn() -> impl Debug { panic!() }
 //~^ ERROR `impl Trait` not allowed outside of function and inherent method return types
+//~| ERROR cannot resolve opaque type
 
 // Disallowed
 fn in_Fn_parameter_in_generics<F: Fn(impl Debug)> (_: F) { panic!() }
diff --git a/src/test/ui/impl-trait/where-allowed.stderr b/src/test/ui/impl-trait/where-allowed.stderr
index 7addc006e19..93f9724140e 100644
--- a/src/test/ui/impl-trait/where-allowed.stderr
+++ b/src/test/ui/impl-trait/where-allowed.stderr
@@ -17,7 +17,7 @@ LL | fn in_impl_Fn_parameter_in_return() -> &'static impl Fn(impl Debug) { panic
    |                                                 outer `impl Trait`
 
 error[E0658]: `impl Trait` in type aliases is unstable
-  --> $DIR/where-allowed.rs:119:16
+  --> $DIR/where-allowed.rs:121:16
    |
 LL |     type Out = impl Debug;
    |                ^^^^^^^^^^
@@ -26,7 +26,7 @@ LL |     type Out = impl Debug;
    = help: add `#![feature(type_alias_impl_trait)]` to the crate attributes to enable
 
 error[E0658]: `impl Trait` in type aliases is unstable
-  --> $DIR/where-allowed.rs:155:23
+  --> $DIR/where-allowed.rs:157:23
    |
 LL | type InTypeAlias<R> = impl Debug;
    |                       ^^^^^^^^^^
@@ -35,7 +35,7 @@ LL | type InTypeAlias<R> = impl Debug;
    = help: add `#![feature(type_alias_impl_trait)]` to the crate attributes to enable
 
 error[E0658]: `impl Trait` in type aliases is unstable
-  --> $DIR/where-allowed.rs:159:39
+  --> $DIR/where-allowed.rs:161:39
    |
 LL | type InReturnInTypeAlias<R> = fn() -> impl Debug;
    |                                       ^^^^^^^^^^
@@ -110,139 +110,139 @@ LL | fn in_impl_Fn_parameter_in_return() -> &'static impl Fn(impl Debug) { panic
    |                                                         ^^^^^^^^^^
 
 error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
-  --> $DIR/where-allowed.rs:61:59
+  --> $DIR/where-allowed.rs:62:59
    |
 LL | fn in_impl_Fn_return_in_return() -> &'static impl Fn() -> impl Debug { panic!() }
    |                                                           ^^^^^^^^^^
 
 error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
-  --> $DIR/where-allowed.rs:65:38
+  --> $DIR/where-allowed.rs:67:38
    |
 LL | fn in_Fn_parameter_in_generics<F: Fn(impl Debug)> (_: F) { panic!() }
    |                                      ^^^^^^^^^^
 
 error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
-  --> $DIR/where-allowed.rs:69:40
+  --> $DIR/where-allowed.rs:71:40
    |
 LL | fn in_Fn_return_in_generics<F: Fn() -> impl Debug> (_: F) { panic!() }
    |                                        ^^^^^^^^^^
 
 error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
-  --> $DIR/where-allowed.rs:82:32
+  --> $DIR/where-allowed.rs:84:32
    |
 LL | struct InBraceStructField { x: impl Debug }
    |                                ^^^^^^^^^^
 
 error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
-  --> $DIR/where-allowed.rs:86:41
+  --> $DIR/where-allowed.rs:88:41
    |
 LL | struct InAdtInBraceStructField { x: Vec<impl Debug> }
    |                                         ^^^^^^^^^^
 
 error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
-  --> $DIR/where-allowed.rs:90:27
+  --> $DIR/where-allowed.rs:92:27
    |
 LL | struct InTupleStructField(impl Debug);
    |                           ^^^^^^^^^^
 
 error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
-  --> $DIR/where-allowed.rs:95:25
+  --> $DIR/where-allowed.rs:97:25
    |
 LL |     InBraceVariant { x: impl Debug },
    |                         ^^^^^^^^^^
 
 error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
-  --> $DIR/where-allowed.rs:97:20
+  --> $DIR/where-allowed.rs:99:20
    |
 LL |     InTupleVariant(impl Debug),
    |                    ^^^^^^^^^^
 
 error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
-  --> $DIR/where-allowed.rs:108:23
+  --> $DIR/where-allowed.rs:110:23
    |
 LL |     fn in_return() -> impl Debug;
    |                       ^^^^^^^^^^
 
 error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
-  --> $DIR/where-allowed.rs:126:34
+  --> $DIR/where-allowed.rs:128:34
    |
 LL |     fn in_trait_impl_return() -> impl Debug { () }
    |                                  ^^^^^^^^^^
 
 error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
-  --> $DIR/where-allowed.rs:139:33
+  --> $DIR/where-allowed.rs:141:33
    |
 LL |     fn in_foreign_parameters(_: impl Debug);
    |                                 ^^^^^^^^^^
 
 error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
-  --> $DIR/where-allowed.rs:142:31
+  --> $DIR/where-allowed.rs:144:31
    |
 LL |     fn in_foreign_return() -> impl Debug;
    |                               ^^^^^^^^^^
 
 error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
-  --> $DIR/where-allowed.rs:159:39
+  --> $DIR/where-allowed.rs:161:39
    |
 LL | type InReturnInTypeAlias<R> = fn() -> impl Debug;
    |                                       ^^^^^^^^^^
 
 error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
-  --> $DIR/where-allowed.rs:164:16
+  --> $DIR/where-allowed.rs:166:16
    |
 LL | impl PartialEq<impl Debug> for () {
    |                ^^^^^^^^^^
 
 error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
-  --> $DIR/where-allowed.rs:169:24
+  --> $DIR/where-allowed.rs:171:24
    |
 LL | impl PartialEq<()> for impl Debug {
    |                        ^^^^^^^^^^
 
 error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
-  --> $DIR/where-allowed.rs:174:6
+  --> $DIR/where-allowed.rs:176:6
    |
 LL | impl impl Debug {
    |      ^^^^^^^^^^
 
 error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
-  --> $DIR/where-allowed.rs:180:24
+  --> $DIR/where-allowed.rs:182:24
    |
 LL | impl InInherentImplAdt<impl Debug> {
    |                        ^^^^^^^^^^
 
 error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
-  --> $DIR/where-allowed.rs:186:11
+  --> $DIR/where-allowed.rs:188:11
    |
 LL |     where impl Debug: Debug
    |           ^^^^^^^^^^
 
 error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
-  --> $DIR/where-allowed.rs:193:15
+  --> $DIR/where-allowed.rs:195:15
    |
 LL |     where Vec<impl Debug>: Debug
    |               ^^^^^^^^^^
 
 error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
-  --> $DIR/where-allowed.rs:200:24
+  --> $DIR/where-allowed.rs:202:24
    |
 LL |     where T: PartialEq<impl Debug>
    |                        ^^^^^^^^^^
 
 error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
-  --> $DIR/where-allowed.rs:207:17
+  --> $DIR/where-allowed.rs:209:17
    |
 LL |     where T: Fn(impl Debug)
    |                 ^^^^^^^^^^
 
 error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
-  --> $DIR/where-allowed.rs:214:22
+  --> $DIR/where-allowed.rs:216:22
    |
 LL |     where T: Fn() -> impl Debug
    |                      ^^^^^^^^^^
 
 error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
-  --> $DIR/where-allowed.rs:220:29
+  --> $DIR/where-allowed.rs:222:29
    |
 LL |     let _in_local_variable: impl Fn() = || {};
    |                             ^^^^^^^^^
@@ -250,24 +250,44 @@ LL |     let _in_local_variable: impl Fn() = || {};
    = help: add `#![feature(impl_trait_in_bindings)]` to the crate attributes to enable
 
 error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
-  --> $DIR/where-allowed.rs:222:46
+  --> $DIR/where-allowed.rs:224:46
    |
 LL |     let _in_return_in_local_variable = || -> impl Fn() { || {} };
    |                                              ^^^^^^^^^
 
+error[E0720]: cannot resolve opaque type
+  --> $DIR/where-allowed.rs:56:49
+   |
+LL | fn in_impl_Fn_parameter_in_return() -> &'static impl Fn(impl Debug) { panic!() }
+   |                                                 ^^^^^^^^^^^^^^^^^^^   -------- this returned value is of `!` type
+   |                                                 |
+   |                                                 cannot resolve opaque type
+   |
+   = help: this error will resolve once the item's body returns a concrete type
+
+error[E0720]: cannot resolve opaque type
+  --> $DIR/where-allowed.rs:62:46
+   |
+LL | fn in_impl_Fn_return_in_return() -> &'static impl Fn() -> impl Debug { panic!() }
+   |                                              ^^^^^^^^^^^^^^^^^^^^^^^   -------- this returned value is of `!` type
+   |                                              |
+   |                                              cannot resolve opaque type
+   |
+   = help: this error will resolve once the item's body returns a concrete type
+
 error: could not find defining uses
-  --> $DIR/where-allowed.rs:119:16
+  --> $DIR/where-allowed.rs:121:16
    |
 LL |     type Out = impl Debug;
    |                ^^^^^^^^^^
 
 error: could not find defining uses
-  --> $DIR/where-allowed.rs:155:23
+  --> $DIR/where-allowed.rs:157:23
    |
 LL | type InTypeAlias<R> = impl Debug;
    |                       ^^^^^^^^^^
 
-error: aborting due to 42 previous errors
+error: aborting due to 44 previous errors
 
-Some errors have detailed explanations: E0562, E0658, E0666.
+Some errors have detailed explanations: E0562, E0658, E0666, E0720.
 For more information about an error, try `rustc --explain E0562`.
diff --git a/src/test/ui/type-alias-impl-trait/bound_reduction2.rs b/src/test/ui/type-alias-impl-trait/bound_reduction2.rs
index 0a4cc9b7fe8..a15074c3593 100644
--- a/src/test/ui/type-alias-impl-trait/bound_reduction2.rs
+++ b/src/test/ui/type-alias-impl-trait/bound_reduction2.rs
@@ -1,19 +1,18 @@
 #![feature(type_alias_impl_trait)]
 
-fn main() {
-}
+fn main() {}
 
 trait TraitWithAssoc {
     type Assoc;
 }
 
 type Foo<V> = impl Trait<V>;
-//~^ ERROR the trait bound `T: TraitWithAssoc` is not satisfied
 
 trait Trait<U> {}
 
 impl<W> Trait<W> for () {}
 
 fn foo_desugared<T: TraitWithAssoc>(_: T) -> Foo<T::Assoc> {
+    //~^ ERROR non-defining opaque type use in defining scope
     ()
 }
diff --git a/src/test/ui/type-alias-impl-trait/bound_reduction2.stderr b/src/test/ui/type-alias-impl-trait/bound_reduction2.stderr
index 9ebf63468e7..c9d6a43b909 100644
--- a/src/test/ui/type-alias-impl-trait/bound_reduction2.stderr
+++ b/src/test/ui/type-alias-impl-trait/bound_reduction2.stderr
@@ -1,14 +1,14 @@
-error[E0277]: the trait bound `T: TraitWithAssoc` is not satisfied
-  --> $DIR/bound_reduction2.rs:10:15
+error: non-defining opaque type use in defining scope
+  --> $DIR/bound_reduction2.rs:15:46
    |
-LL | type Foo<V> = impl Trait<V>;
-   |               ^^^^^^^^^^^^^ the trait `TraitWithAssoc` is not implemented for `T`
+LL | fn foo_desugared<T: TraitWithAssoc>(_: T) -> Foo<T::Assoc> {
+   |                                              ^^^^^^^^^^^^^
    |
-help: consider further restricting this bound
+note: used non-generic type `<T as TraitWithAssoc>::Assoc` for generic parameter
+  --> $DIR/bound_reduction2.rs:9:10
    |
-LL | fn foo_desugared<T: TraitWithAssoc + TraitWithAssoc>(_: T) -> Foo<T::Assoc> {
-   |                                    ^^^^^^^^^^^^^^^^
+LL | type Foo<V> = impl Trait<V>;
+   |          ^
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0277`.
diff --git a/src/test/ui/type-alias-impl-trait/declared_but_not_defined_in_scope.rs b/src/test/ui/type-alias-impl-trait/declared_but_not_defined_in_scope.rs
index 09873a8c8c3..7ea517eb734 100644
--- a/src/test/ui/type-alias-impl-trait/declared_but_not_defined_in_scope.rs
+++ b/src/test/ui/type-alias-impl-trait/declared_but_not_defined_in_scope.rs
@@ -9,4 +9,5 @@ mod boo {
 
 fn bomp() -> boo::Boo {
     ""
+    //~^ mismatched types
 }
diff --git a/src/test/ui/type-alias-impl-trait/declared_but_not_defined_in_scope.stderr b/src/test/ui/type-alias-impl-trait/declared_but_not_defined_in_scope.stderr
index c0cb94b15d0..0b4c262bbb4 100644
--- a/src/test/ui/type-alias-impl-trait/declared_but_not_defined_in_scope.stderr
+++ b/src/test/ui/type-alias-impl-trait/declared_but_not_defined_in_scope.stderr
@@ -4,5 +4,20 @@ error: could not find defining uses
 LL |     pub type Boo = impl ::std::fmt::Debug;
    |                    ^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to previous error
+error[E0308]: mismatched types
+  --> $DIR/declared_but_not_defined_in_scope.rs:11:5
+   |
+LL |     pub type Boo = impl ::std::fmt::Debug;
+   |                    ---------------------- the expected opaque type
+...
+LL | fn bomp() -> boo::Boo {
+   |              -------- expected `impl Debug` because of return type
+LL |     ""
+   |     ^^ expected opaque type, found `&str`
+   |
+   = note: expected opaque type `impl Debug`
+                found reference `&'static str`
+
+error: aborting due to 2 previous errors
 
+For more information about this error, try `rustc --explain E0308`.
diff --git a/src/test/ui/type-alias-impl-trait/generic_duplicate_param_use2.rs b/src/test/ui/type-alias-impl-trait/generic_duplicate_param_use2.rs
index 2b98d8fc63a..a74731df695 100644
--- a/src/test/ui/type-alias-impl-trait/generic_duplicate_param_use2.rs
+++ b/src/test/ui/type-alias-impl-trait/generic_duplicate_param_use2.rs
@@ -8,10 +8,10 @@ fn main() {}
 type Two<T, U> = impl Debug;
 
 fn one<T: Debug>(t: T) -> Two<T, T> {
+    //~^ ERROR non-defining opaque type use in defining scope
     t
 }
 
 fn two<T: Debug, U>(t: T, _: U) -> Two<T, U> {
-//~^ ERROR concrete type differs from previous defining opaque type use
     t
 }
diff --git a/src/test/ui/type-alias-impl-trait/generic_duplicate_param_use2.stderr b/src/test/ui/type-alias-impl-trait/generic_duplicate_param_use2.stderr
index 7900da47ca2..d87e8c5783b 100644
--- a/src/test/ui/type-alias-impl-trait/generic_duplicate_param_use2.stderr
+++ b/src/test/ui/type-alias-impl-trait/generic_duplicate_param_use2.stderr
@@ -1,14 +1,14 @@
-error: concrete type differs from previous defining opaque type use
-  --> $DIR/generic_duplicate_param_use2.rs:14:1
+error: non-defining opaque type use in defining scope
+  --> $DIR/generic_duplicate_param_use2.rs:10:27
    |
-LL | fn two<T: Debug, U>(t: T, _: U) -> Two<T, U> {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `U`, got `T`
+LL | fn one<T: Debug>(t: T) -> Two<T, T> {
+   |                           ^^^^^^^^^
    |
-note: previous use here
-  --> $DIR/generic_duplicate_param_use2.rs:10:1
+note: type used multiple times
+  --> $DIR/generic_duplicate_param_use2.rs:8:10
    |
-LL | fn one<T: Debug>(t: T) -> Two<T, T> {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | type Two<T, U> = impl Debug;
+   |          ^  ^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/type-alias-impl-trait/generic_duplicate_param_use3.rs b/src/test/ui/type-alias-impl-trait/generic_duplicate_param_use3.rs
index d9133fd11f7..0597b8385d2 100644
--- a/src/test/ui/type-alias-impl-trait/generic_duplicate_param_use3.rs
+++ b/src/test/ui/type-alias-impl-trait/generic_duplicate_param_use3.rs
@@ -8,11 +8,11 @@ fn main() {}
 type Two<T, U> = impl Debug;
 
 fn one<T: Debug>(t: T) -> Two<T, T> {
+    //~^ ERROR non-defining opaque type use in defining scope
     t
 }
 
 fn two<T: Debug, U>(t: T, _: U) -> Two<T, U> {
-//~^ ERROR concrete type differs from previous defining opaque type use
     t
 }
 
diff --git a/src/test/ui/type-alias-impl-trait/generic_duplicate_param_use3.stderr b/src/test/ui/type-alias-impl-trait/generic_duplicate_param_use3.stderr
index ac5f7947d51..711de855f0d 100644
--- a/src/test/ui/type-alias-impl-trait/generic_duplicate_param_use3.stderr
+++ b/src/test/ui/type-alias-impl-trait/generic_duplicate_param_use3.stderr
@@ -1,14 +1,14 @@
-error: concrete type differs from previous defining opaque type use
-  --> $DIR/generic_duplicate_param_use3.rs:14:1
+error: non-defining opaque type use in defining scope
+  --> $DIR/generic_duplicate_param_use3.rs:10:27
    |
-LL | fn two<T: Debug, U>(t: T, _: U) -> Two<T, U> {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `U`, got `T`
+LL | fn one<T: Debug>(t: T) -> Two<T, T> {
+   |                           ^^^^^^^^^
    |
-note: previous use here
-  --> $DIR/generic_duplicate_param_use3.rs:10:1
+note: type used multiple times
+  --> $DIR/generic_duplicate_param_use3.rs:8:10
    |
-LL | fn one<T: Debug>(t: T) -> Two<T, T> {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | type Two<T, U> = impl Debug;
+   |          ^  ^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/type-alias-impl-trait/generic_underconstrained.rs b/src/test/ui/type-alias-impl-trait/generic_underconstrained.rs
index 589612d5ed6..766ee36c02b 100644
--- a/src/test/ui/type-alias-impl-trait/generic_underconstrained.rs
+++ b/src/test/ui/type-alias-impl-trait/generic_underconstrained.rs
@@ -3,10 +3,11 @@
 fn main() {}
 
 trait Trait {}
-type Underconstrained<T: Trait> = impl 'static; //~ ERROR the trait bound `T: Trait`
+type Underconstrained<T: Trait> = impl 'static;
 //~^ ERROR: at least one trait must be specified
 
 // no `Trait` bound
 fn underconstrain<T>(_: T) -> Underconstrained<T> {
+    //~^ ERROR the trait bound `T: Trait`
     unimplemented!()
 }
diff --git a/src/test/ui/type-alias-impl-trait/generic_underconstrained.stderr b/src/test/ui/type-alias-impl-trait/generic_underconstrained.stderr
index 911f592f73f..cefc5d99b37 100644
--- a/src/test/ui/type-alias-impl-trait/generic_underconstrained.stderr
+++ b/src/test/ui/type-alias-impl-trait/generic_underconstrained.stderr
@@ -5,12 +5,14 @@ LL | type Underconstrained<T: Trait> = impl 'static;
    |                                   ^^^^^^^^^^^^
 
 error[E0277]: the trait bound `T: Trait` is not satisfied
-  --> $DIR/generic_underconstrained.rs:6:35
+  --> $DIR/generic_underconstrained.rs:10:31
    |
 LL | type Underconstrained<T: Trait> = impl 'static;
-   |                                   ^^^^^^^^^^^^ the trait `Trait` is not implemented for `T`
+   |                          ----- required by this bound in `Underconstrained`
+...
+LL | fn underconstrain<T>(_: T) -> Underconstrained<T> {
+   |                               ^^^^^^^^^^^^^^^^^^^ the trait `Trait` is not implemented for `T`
    |
-   = note: the return type of a function must have a statically known size
 help: consider restricting type parameter `T`
    |
 LL | fn underconstrain<T: Trait>(_: T) -> Underconstrained<T> {
diff --git a/src/test/ui/type-alias-impl-trait/generic_underconstrained2.rs b/src/test/ui/type-alias-impl-trait/generic_underconstrained2.rs
index 4ac32e8a870..cd7c962e2d1 100644
--- a/src/test/ui/type-alias-impl-trait/generic_underconstrained2.rs
+++ b/src/test/ui/type-alias-impl-trait/generic_underconstrained2.rs
@@ -3,19 +3,19 @@
 fn main() {}
 
 type Underconstrained<T: std::fmt::Debug> = impl 'static;
-//~^ ERROR `U` doesn't implement `Debug`
-//~^^ ERROR: at least one trait must be specified
+//~^ ERROR: at least one trait must be specified
 
 // not a defining use, because it doesn't define *all* possible generics
 fn underconstrained<U>(_: U) -> Underconstrained<U> {
+    //~^ ERROR `U` doesn't implement `Debug`
     5u32
 }
 
 type Underconstrained2<T: std::fmt::Debug> = impl 'static;
-//~^ ERROR `V` doesn't implement `Debug`
-//~^^ ERROR: at least one trait must be specified
+//~^ ERROR: at least one trait must be specified
 
 // not a defining use, because it doesn't define *all* possible generics
 fn underconstrained2<U, V>(_: U, _: V) -> Underconstrained2<V> {
+    //~^ ERROR `V` doesn't implement `Debug`
     5u32
 }
diff --git a/src/test/ui/type-alias-impl-trait/generic_underconstrained2.stderr b/src/test/ui/type-alias-impl-trait/generic_underconstrained2.stderr
index 5ff82d4ad25..669546aef86 100644
--- a/src/test/ui/type-alias-impl-trait/generic_underconstrained2.stderr
+++ b/src/test/ui/type-alias-impl-trait/generic_underconstrained2.stderr
@@ -11,30 +11,28 @@ LL | type Underconstrained2<T: std::fmt::Debug> = impl 'static;
    |                                              ^^^^^^^^^^^^
 
 error[E0277]: `U` doesn't implement `Debug`
-  --> $DIR/generic_underconstrained2.rs:5:45
+  --> $DIR/generic_underconstrained2.rs:9:33
    |
 LL | type Underconstrained<T: std::fmt::Debug> = impl 'static;
-   |                                             ^^^^^^^^^^^^ `U` cannot be formatted using `{:?}` because it doesn't implement `Debug`
+   |                          --------------- required by this bound in `Underconstrained`
 ...
-LL |     5u32
-   |     ---- this returned value is of type `u32`
+LL | fn underconstrained<U>(_: U) -> Underconstrained<U> {
+   |                                 ^^^^^^^^^^^^^^^^^^^ `U` cannot be formatted using `{:?}` because it doesn't implement `Debug`
    |
-   = note: the return type of a function must have a statically known size
 help: consider restricting type parameter `U`
    |
 LL | fn underconstrained<U: Debug>(_: U) -> Underconstrained<U> {
    |                      ^^^^^^^
 
 error[E0277]: `V` doesn't implement `Debug`
-  --> $DIR/generic_underconstrained2.rs:14:46
+  --> $DIR/generic_underconstrained2.rs:18:43
    |
 LL | type Underconstrained2<T: std::fmt::Debug> = impl 'static;
-   |                                              ^^^^^^^^^^^^ `V` cannot be formatted using `{:?}` because it doesn't implement `Debug`
+   |                           --------------- required by this bound in `Underconstrained2`
 ...
-LL |     5u32
-   |     ---- this returned value is of type `u32`
+LL | fn underconstrained2<U, V>(_: U, _: V) -> Underconstrained2<V> {
+   |                                           ^^^^^^^^^^^^^^^^^^^^ `V` cannot be formatted using `{:?}` because it doesn't implement `Debug`
    |
-   = note: the return type of a function must have a statically known size
 help: consider restricting type parameter `V`
    |
 LL | fn underconstrained2<U, V: Debug>(_: U, _: V) -> Underconstrained2<V> {
diff --git a/src/test/ui/type-alias-impl-trait/impl-with-unconstrained-param.rs b/src/test/ui/type-alias-impl-trait/impl-with-unconstrained-param.rs
index bc6543a9229..851c2f66c47 100644
--- a/src/test/ui/type-alias-impl-trait/impl-with-unconstrained-param.rs
+++ b/src/test/ui/type-alias-impl-trait/impl-with-unconstrained-param.rs
@@ -9,10 +9,9 @@ trait X {
 }
 
 impl<T> X for () {
+    //~^ ERROR the type parameter `T` is not constrained
     type I = impl Sized;
-    //~^ ERROR could not find defining uses
     fn f() -> Self::I {}
-    //~^ ERROR type annotations needed
 }
 
 fn main() {}
diff --git a/src/test/ui/type-alias-impl-trait/impl-with-unconstrained-param.stderr b/src/test/ui/type-alias-impl-trait/impl-with-unconstrained-param.stderr
index e8b677113db..8cf8fb1d16c 100644
--- a/src/test/ui/type-alias-impl-trait/impl-with-unconstrained-param.stderr
+++ b/src/test/ui/type-alias-impl-trait/impl-with-unconstrained-param.stderr
@@ -1,15 +1,9 @@
-error[E0282]: type annotations needed
-  --> $DIR/impl-with-unconstrained-param.rs:14:23
+error[E0207]: the type parameter `T` is not constrained by the impl trait, self type, or predicates
+  --> $DIR/impl-with-unconstrained-param.rs:11:6
    |
-LL |     fn f() -> Self::I {}
-   |                       ^^ cannot infer type for type parameter `T`
+LL | impl<T> X for () {
+   |      ^ unconstrained type parameter
 
-error: could not find defining uses
-  --> $DIR/impl-with-unconstrained-param.rs:12:14
-   |
-LL |     type I = impl Sized;
-   |              ^^^^^^^^^^
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0282`.
+For more information about this error, try `rustc --explain E0207`.
diff --git a/src/test/ui/type-alias-impl-trait/issue-57611-trait-alias.rs b/src/test/ui/type-alias-impl-trait/issue-57611-trait-alias.rs
index 41e019247c9..782eb0fb3df 100644
--- a/src/test/ui/type-alias-impl-trait/issue-57611-trait-alias.rs
+++ b/src/test/ui/type-alias-impl-trait/issue-57611-trait-alias.rs
@@ -22,6 +22,6 @@ impl Foo for X {
     }
 }
 
-trait Baz<A, B> = Fn(&A) -> &B;
+trait Baz<A: ?Sized, B: ?Sized> = Fn(&A) -> &B;
 
 fn main() {}
diff --git a/src/test/ui/type-alias-impl-trait/not_a_defining_use.rs b/src/test/ui/type-alias-impl-trait/not_a_defining_use.rs
index 02485b24e7b..f29b980dfd0 100644
--- a/src/test/ui/type-alias-impl-trait/not_a_defining_use.rs
+++ b/src/test/ui/type-alias-impl-trait/not_a_defining_use.rs
@@ -7,6 +7,7 @@ fn main() {}
 type Two<T, U> = impl Debug;
 
 fn two<T: Debug>(t: T) -> Two<T, u32> {
+    //~^ ERROR non-defining opaque type use in defining scope
     (t, 4i8)
 }
 
@@ -24,9 +25,7 @@ impl Bar for u32 {
     const FOO: i32 = 42;
 }
 
-// this should work! But it requires `two` and `three` not to be defining uses,
-// just restricting uses
-fn four<T: Debug, U: Bar>(t: T) -> Two<T, U> { //~ concrete type differs from previous
+fn four<T: Debug, U: Bar>(t: T) -> Two<T, U> {
     (t, <U as Bar>::FOO)
 }
 
diff --git a/src/test/ui/type-alias-impl-trait/not_a_defining_use.stderr b/src/test/ui/type-alias-impl-trait/not_a_defining_use.stderr
index 9ce07a879f0..2fa236b373a 100644
--- a/src/test/ui/type-alias-impl-trait/not_a_defining_use.stderr
+++ b/src/test/ui/type-alias-impl-trait/not_a_defining_use.stderr
@@ -1,14 +1,14 @@
-error: concrete type differs from previous defining opaque type use
-  --> $DIR/not_a_defining_use.rs:29:1
+error: non-defining opaque type use in defining scope
+  --> $DIR/not_a_defining_use.rs:9:27
    |
-LL | fn four<T: Debug, U: Bar>(t: T) -> Two<T, U> {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `(T, i8)`, got `(T, <U as Bar>::Blub)`
+LL | fn two<T: Debug>(t: T) -> Two<T, u32> {
+   |                           ^^^^^^^^^^^
    |
-note: previous use here
-  --> $DIR/not_a_defining_use.rs:9:1
+note: used non-generic type `u32` for generic parameter
+  --> $DIR/not_a_defining_use.rs:7:13
    |
-LL | fn two<T: Debug>(t: T) -> Two<T, u32> {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | type Two<T, U> = impl Debug;
+   |             ^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/type-alias-impl-trait/type-alias-impl-trait-unconstrained-lifetime.rs b/src/test/ui/type-alias-impl-trait/type-alias-impl-trait-unconstrained-lifetime.rs
new file mode 100644
index 00000000000..efbf4f1e351
--- /dev/null
+++ b/src/test/ui/type-alias-impl-trait/type-alias-impl-trait-unconstrained-lifetime.rs
@@ -0,0 +1,18 @@
+// regression test for #74018
+
+#![feature(type_alias_impl_trait)]
+
+trait Trait {
+    type Associated;
+    fn into(self) -> Self::Associated;
+}
+
+impl<'a, I: Iterator<Item = i32>> Trait for (i32, I) {
+    //~^ ERROR the lifetime parameter `'a` is not constrained
+    type Associated = (i32, impl Iterator<Item = i32>);
+    fn into(self) -> Self::Associated {
+        (0_i32, [0_i32].iter().copied())
+    }
+}
+
+fn main() {}
diff --git a/src/test/ui/type-alias-impl-trait/type-alias-impl-trait-unconstrained-lifetime.stderr b/src/test/ui/type-alias-impl-trait/type-alias-impl-trait-unconstrained-lifetime.stderr
new file mode 100644
index 00000000000..8cdce2f8e81
--- /dev/null
+++ b/src/test/ui/type-alias-impl-trait/type-alias-impl-trait-unconstrained-lifetime.stderr
@@ -0,0 +1,9 @@
+error[E0207]: the lifetime parameter `'a` is not constrained by the impl trait, self type, or predicates
+  --> $DIR/type-alias-impl-trait-unconstrained-lifetime.rs:10:6
+   |
+LL | impl<'a, I: Iterator<Item = i32>> Trait for (i32, I) {
+   |      ^^ unconstrained lifetime parameter
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0207`.
diff --git a/src/test/ui/typeck/typeck_type_placeholder_item.stderr b/src/test/ui/typeck/typeck_type_placeholder_item.stderr
index 48ff1a2c513..684f451b7c3 100644
--- a/src/test/ui/typeck/typeck_type_placeholder_item.stderr
+++ b/src/test/ui/typeck/typeck_type_placeholder_item.stderr
@@ -405,15 +405,10 @@ LL | type X = Box<_>;
    |              ^ not allowed in type signatures
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:43:27
-   |
-LL |     fn test10(&self, _x : _) { }
-   |                           ^ not allowed in type signatures
-   |
-help: use type parameters instead
+  --> $DIR/typeck_type_placeholder_item.rs:182:21
    |
-LL |     fn test10<T>(&self, _x : T) { }
-   |              ^^^             ^
+LL | type Y = impl Trait<_>;
+   |                     ^ not allowed in type signatures
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
   --> $DIR/typeck_type_placeholder_item.rs:140:31
@@ -486,45 +481,6 @@ LL |     fn assoc_fn_test3<T>() -> T;
    |                      ^^^      ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:61:37
-   |
-LL |     fn clone_from(&mut self, other: _) { *self = Test9; }
-   |                                     ^ not allowed in type signatures
-   |
-help: use type parameters instead
-   |
-LL |     fn clone_from<T>(&mut self, other: T) { *self = Test9; }
-   |                  ^^^                   ^
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:110:34
-   |
-LL |         fn fn_test10(&self, _x : _) { }
-   |                                  ^ not allowed in type signatures
-   |
-help: use type parameters instead
-   |
-LL |         fn fn_test10<T>(&self, _x : T) { }
-   |                     ^^^             ^
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:118:41
-   |
-LL |         fn clone_from(&mut self, other: _) { *self = FnTest9; }
-   |                                         ^ not allowed in type signatures
-   |
-help: use type parameters instead
-   |
-LL |         fn clone_from<T>(&mut self, other: T) { *self = FnTest9; }
-   |                      ^^^                   ^
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:182:21
-   |
-LL | type Y = impl Trait<_>;
-   |                     ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
   --> $DIR/typeck_type_placeholder_item.rs:190:14
    |
 LL |     type B = _;
@@ -561,6 +517,17 @@ LL |     fn test9(&self) -> _ { () }
    |                        help: replace with the correct return type: `()`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
+  --> $DIR/typeck_type_placeholder_item.rs:43:27
+   |
+LL |     fn test10(&self, _x : _) { }
+   |                           ^ not allowed in type signatures
+   |
+help: use type parameters instead
+   |
+LL |     fn test10<T>(&self, _x : T) { }
+   |              ^^^             ^
+
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures
   --> $DIR/typeck_type_placeholder_item.rs:58:24
    |
 LL |     fn clone(&self) -> _ { Test9 }
@@ -570,6 +537,17 @@ LL |     fn clone(&self) -> _ { Test9 }
    |                        help: replace with the correct return type: `Test9`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
+  --> $DIR/typeck_type_placeholder_item.rs:61:37
+   |
+LL |     fn clone_from(&mut self, other: _) { *self = Test9; }
+   |                                     ^ not allowed in type signatures
+   |
+help: use type parameters instead
+   |
+LL |     fn clone_from<T>(&mut self, other: T) { *self = Test9; }
+   |                  ^^^                   ^
+
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures
   --> $DIR/typeck_type_placeholder_item.rs:107:31
    |
 LL |         fn fn_test9(&self) -> _ { () }
@@ -579,6 +557,17 @@ LL |         fn fn_test9(&self) -> _ { () }
    |                               help: replace with the correct return type: `()`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
+  --> $DIR/typeck_type_placeholder_item.rs:110:34
+   |
+LL |         fn fn_test10(&self, _x : _) { }
+   |                                  ^ not allowed in type signatures
+   |
+help: use type parameters instead
+   |
+LL |         fn fn_test10<T>(&self, _x : T) { }
+   |                     ^^^             ^
+
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures
   --> $DIR/typeck_type_placeholder_item.rs:115:28
    |
 LL |         fn clone(&self) -> _ { FnTest9 }
@@ -588,6 +577,17 @@ LL |         fn clone(&self) -> _ { FnTest9 }
    |                            help: replace with the correct return type: `FnTest9`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
+  --> $DIR/typeck_type_placeholder_item.rs:118:41
+   |
+LL |         fn clone_from(&mut self, other: _) { *self = FnTest9; }
+   |                                         ^ not allowed in type signatures
+   |
+help: use type parameters instead
+   |
+LL |         fn clone_from<T>(&mut self, other: T) { *self = FnTest9; }
+   |                      ^^^                   ^
+
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures
   --> $DIR/typeck_type_placeholder_item.rs:201:14
    |
 LL |     type A = _;