Tweak output

- Only point at a the single expression where the found type was first
  inferred.
- Find method call argument that might have caused the found type to be
  inferred.
- Provide structured suggestion.
- Apply some review comments.
- Tweak wording.

6 files changed, 124 insertions, 12 deletions

diff --git a/src/test/ui/type/type-check/assignment-in-if.stderr b/src/test/ui/type/type-check/assignment-in-if.stderr
index fb11d6160bb..de133e5599c 100644
--- a/src/test/ui/type/type-check/assignment-in-if.stderr
+++ b/src/test/ui/type/type-check/assignment-in-if.stderr
@@ -67,10 +67,7 @@ LL |             x == 5
 error[E0308]: mismatched types
   --> $DIR/assignment-in-if.rs:44:18
    |
-LL |     let x = 1;
-   |             - here the type of `x` is inferred to be `{integer}`
-...
-LL |         println!("{}", x);
+LL |     if y = (Foo { foo: x }) {
    |                        - here the type of `x` is inferred to be `usize`
 ...
 LL |     if x == x && x = x && x == x {
@@ -81,10 +78,7 @@ LL |     if x == x && x = x && x == x {
 error[E0308]: mismatched types
   --> $DIR/assignment-in-if.rs:44:22
    |
-LL |     let x = 1;
-   |             - here the type of `x` is inferred to be `{integer}`
-...
-LL |         println!("{}", x);
+LL |     if y = (Foo { foo: x }) {
    |                        - here the type of `x` is inferred to be `usize`
 ...
 LL |     if x == x && x = x && x == x {
@@ -104,10 +98,7 @@ LL |     if x == x && x == x && x == x {
 error[E0308]: mismatched types
   --> $DIR/assignment-in-if.rs:51:28
    |
-LL |     let x = 1;
-   |             - here the type of `x` is inferred to be `{integer}`
-...
-LL |         println!("{}", x);
+LL |     if y = (Foo { foo: x }) {
    |                        - here the type of `x` is inferred to be `usize`
 ...
 LL |     if x == x && x == x && x = x {
diff --git a/src/test/ui/type/type-check/point-at-inference-2.rs b/src/test/ui/type/type-check/point-at-inference-2.rs
new file mode 100644
index 00000000000..6557d7fa191
--- /dev/null
+++ b/src/test/ui/type/type-check/point-at-inference-2.rs
@@ -0,0 +1,13 @@
+fn bar(_: Vec<i32>) {}
+fn baz(_: &Vec<&i32>) {}
+fn main() {
+    let v = vec![&1];
+    bar(v); //~ ERROR E0308
+    let v = vec![];
+    baz(&v);
+    baz(&v);
+    bar(v); //~ ERROR E0308
+    let v = vec![];
+    baz(&v);
+    bar(v); //~ ERROR E0308
+}
diff --git a/src/test/ui/type/type-check/point-at-inference-2.stderr b/src/test/ui/type/type-check/point-at-inference-2.stderr
new file mode 100644
index 00000000000..13227c5e245
--- /dev/null
+++ b/src/test/ui/type/type-check/point-at-inference-2.stderr
@@ -0,0 +1,56 @@
+error[E0308]: mismatched types
+  --> $DIR/point-at-inference-2.rs:5:9
+   |
+LL |     bar(v);
+   |     --- ^ expected `i32`, found `&{integer}`
+   |     |
+   |     arguments to this function are incorrect
+   |
+   = note: expected struct `Vec<i32>`
+              found struct `Vec<&{integer}>`
+note: function defined here
+  --> $DIR/point-at-inference-2.rs:1:4
+   |
+LL | fn bar(_: Vec<i32>) {}
+   |    ^^^ -----------
+
+error[E0308]: mismatched types
+  --> $DIR/point-at-inference-2.rs:9:9
+   |
+LL |     baz(&v);
+   |          - here the type of `v` is inferred to be `Vec<&i32>`
+LL |     baz(&v);
+LL |     bar(v);
+   |     --- ^ expected `i32`, found `&i32`
+   |     |
+   |     arguments to this function are incorrect
+   |
+   = note: expected struct `Vec<i32>`
+              found struct `Vec<&i32>`
+note: function defined here
+  --> $DIR/point-at-inference-2.rs:1:4
+   |
+LL | fn bar(_: Vec<i32>) {}
+   |    ^^^ -----------
+
+error[E0308]: mismatched types
+  --> $DIR/point-at-inference-2.rs:12:9
+   |
+LL |     baz(&v);
+   |          - here the type of `v` is inferred to be `Vec<&i32>`
+LL |     bar(v);
+   |     --- ^ expected `i32`, found `&i32`
+   |     |
+   |     arguments to this function are incorrect
+   |
+   = note: expected struct `Vec<i32>`
+              found struct `Vec<&i32>`
+note: function defined here
+  --> $DIR/point-at-inference-2.rs:1:4
+   |
+LL | fn bar(_: Vec<i32>) {}
+   |    ^^^ -----------
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/src/test/ui/type/type-check/point-at-inference.fixed b/src/test/ui/type/type-check/point-at-inference.fixed
new file mode 100644
index 00000000000..f41fbe59fba
--- /dev/null
+++ b/src/test/ui/type/type-check/point-at-inference.fixed
@@ -0,0 +1,13 @@
+// run-rustfix
+fn bar(_: Vec<i32>) {}
+fn baz(_: &impl std::any::Any) {}
+fn main() {
+    let v = vec![1, 2, 3, 4, 5];
+    let mut foo = vec![];
+    baz(&foo);
+    for i in &v {
+        foo.push(*i);
+    }
+    baz(&foo);
+    bar(foo); //~ ERROR E0308
+}
diff --git a/src/test/ui/type/type-check/point-at-inference.rs b/src/test/ui/type/type-check/point-at-inference.rs
new file mode 100644
index 00000000000..6419e42e70d
--- /dev/null
+++ b/src/test/ui/type/type-check/point-at-inference.rs
@@ -0,0 +1,13 @@
+// run-rustfix
+fn bar(_: Vec<i32>) {}
+fn baz(_: &impl std::any::Any) {}
+fn main() {
+    let v = vec![1, 2, 3, 4, 5];
+    let mut foo = vec![];
+    baz(&foo);
+    for i in &v {
+        foo.push(i);
+    }
+    baz(&foo);
+    bar(foo); //~ ERROR E0308
+}
diff --git a/src/test/ui/type/type-check/point-at-inference.stderr b/src/test/ui/type/type-check/point-at-inference.stderr
new file mode 100644
index 00000000000..197511bf64e
--- /dev/null
+++ b/src/test/ui/type/type-check/point-at-inference.stderr
@@ -0,0 +1,26 @@
+error[E0308]: mismatched types
+  --> $DIR/point-at-inference.rs:12:9
+   |
+LL |         foo.push(i);
+   |                  - this is of type `&{integer}`, which makes `foo` to be inferred as `Vec<&{integer}>`
+...
+LL |     bar(foo);
+   |     --- ^^^ expected `i32`, found `&{integer}`
+   |     |
+   |     arguments to this function are incorrect
+   |
+   = note: expected struct `Vec<i32>`
+              found struct `Vec<&{integer}>`
+note: function defined here
+  --> $DIR/point-at-inference.rs:2:4
+   |
+LL | fn bar(_: Vec<i32>) {}
+   |    ^^^ -----------
+help: consider dereferencing the borrow
+   |
+LL |         foo.push(*i);
+   |                  +
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.