Rollup merge of #141812 - JonathanBrouwer:fix-else-if-help, r=jdonszelmann

Fix "consider borrowing" for else-if

Fixes rust-lang/rust#141810

When trying to suggest a borrow on a `if` or `block` expression, instead we now recurse into the `if` or `block`.
The comments in the code should explain the goal of the new code.

r? ``@jdonszelmann``

8 files changed, 118 insertions, 0 deletions

diff --git a/tests/ui/typeck/consider-borrowing-141810-1.rs b/tests/ui/typeck/consider-borrowing-141810-1.rs
new file mode 100644
index 00000000000..94c2d690915
--- /dev/null
+++ b/tests/ui/typeck/consider-borrowing-141810-1.rs
@@ -0,0 +1,9 @@
+fn main() {
+    let x = if true {
+        &true
+    } else if false { //~ ERROR `if` and `else` have incompatible types [E0308]
+        true //~ HELP consider borrowing here
+    } else {
+        true
+    };
+}
diff --git a/tests/ui/typeck/consider-borrowing-141810-1.stderr b/tests/ui/typeck/consider-borrowing-141810-1.stderr
new file mode 100644
index 00000000000..9291721ac71
--- /dev/null
+++ b/tests/ui/typeck/consider-borrowing-141810-1.stderr
@@ -0,0 +1,28 @@
+error[E0308]: `if` and `else` have incompatible types
+  --> $DIR/consider-borrowing-141810-1.rs:4:12
+   |
+LL |        let x = if true {
+   |  ______________-
+LL | |          &true
+   | |          ----- expected because of this
+LL | |      } else if false {
+   | | ____________^
+LL | ||         true
+LL | ||     } else {
+LL | ||         true
+LL | ||     };
+   | ||     ^
+   | ||_____|
+   |  |_____`if` and `else` have incompatible types
+   |        expected `&bool`, found `bool`
+   |
+help: consider borrowing here
+   |
+LL ~         &true
+LL |     } else {
+LL ~         &true
+   |
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/typeck/consider-borrowing-141810-2.rs b/tests/ui/typeck/consider-borrowing-141810-2.rs
new file mode 100644
index 00000000000..e32e689efb7
--- /dev/null
+++ b/tests/ui/typeck/consider-borrowing-141810-2.rs
@@ -0,0 +1,8 @@
+fn main() {
+    let x = if true {
+        &()
+    } else if false { //~ ERROR `if` and `else` have incompatible types [E0308]
+    } else {
+    };
+
+}
diff --git a/tests/ui/typeck/consider-borrowing-141810-2.stderr b/tests/ui/typeck/consider-borrowing-141810-2.stderr
new file mode 100644
index 00000000000..dd229897283
--- /dev/null
+++ b/tests/ui/typeck/consider-borrowing-141810-2.stderr
@@ -0,0 +1,19 @@
+error[E0308]: `if` and `else` have incompatible types
+  --> $DIR/consider-borrowing-141810-2.rs:4:12
+   |
+LL |        let x = if true {
+   |  ______________-
+LL | |          &()
+   | |          --- expected because of this
+LL | |      } else if false {
+   | | ____________^
+LL | ||     } else {
+LL | ||     };
+   | ||     ^
+   | ||_____|
+   |  |_____`if` and `else` have incompatible types
+   |        expected `&()`, found `()`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/typeck/consider-borrowing-141810-3.rs b/tests/ui/typeck/consider-borrowing-141810-3.rs
new file mode 100644
index 00000000000..d38828de7c1
--- /dev/null
+++ b/tests/ui/typeck/consider-borrowing-141810-3.rs
@@ -0,0 +1,7 @@
+fn main() {
+    let x = if true {
+        &()
+    } else if false { //~ ERROR `if` and `else` have incompatible types [E0308]
+
+    };
+}
diff --git a/tests/ui/typeck/consider-borrowing-141810-3.stderr b/tests/ui/typeck/consider-borrowing-141810-3.stderr
new file mode 100644
index 00000000000..0b0c5f191a0
--- /dev/null
+++ b/tests/ui/typeck/consider-borrowing-141810-3.stderr
@@ -0,0 +1,22 @@
+error[E0308]: `if` and `else` have incompatible types
+  --> $DIR/consider-borrowing-141810-3.rs:4:12
+   |
+LL |        let x = if true {
+   |  ______________-
+LL | |          &()
+   | |          --- expected because of this
+LL | |      } else if false {
+   | | ____________^
+LL | ||
+LL | ||     };
+   | ||     ^
+   | ||_____|
+   |  |_____`if` and `else` have incompatible types
+   |        expected `&()`, found `()`
+   |
+   = note: `if` expressions without `else` evaluate to `()`
+   = note: consider adding an `else` block that evaluates to the expected type
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/typeck/consider-borrowing-141810-4.rs b/tests/ui/typeck/consider-borrowing-141810-4.rs
new file mode 100644
index 00000000000..754af7920a8
--- /dev/null
+++ b/tests/ui/typeck/consider-borrowing-141810-4.rs
@@ -0,0 +1,11 @@
+fn baz(x: &String) {}
+
+fn bar() {
+    baz({
+        String::from("hi") //~ ERROR mismatched types
+    });
+}
+
+fn main() {
+    bar();
+}
diff --git a/tests/ui/typeck/consider-borrowing-141810-4.stderr b/tests/ui/typeck/consider-borrowing-141810-4.stderr
new file mode 100644
index 00000000000..80869d4a5d5
--- /dev/null
+++ b/tests/ui/typeck/consider-borrowing-141810-4.stderr
@@ -0,0 +1,14 @@
+error[E0308]: mismatched types
+  --> $DIR/consider-borrowing-141810-4.rs:5:9
+   |
+LL |         String::from("hi")
+   |         ^^^^^^^^^^^^^^^^^^ expected `&String`, found `String`
+   |
+help: consider borrowing here
+   |
+LL |         &String::from("hi")
+   |         +
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.