Rollup merge of #57723 - estebank:fix, r=davidtwco

Point at cause for expectation in return type type error

Various improvements and fixes for type errors in return expressions.

Fix #57664.

src/test/ui/fully-qualified-type/fully-qualified-type-name2.stderr

@@ -1,6 +1,8 @@
 error[E0308]: mismatched types
   --> $DIR/fully-qualified-type-name2.rs:12:12
    |
+LL | fn bar(x: x::Foo) -> y::Foo {
+   |                      ------ expected `y::Foo` because of return type
 LL |     return x;
    |            ^ expected enum `y::Foo`, found enum `x::Foo`
    |

src/test/ui/fully-qualified-type/fully-qualified-type-name4.stderr

@@ -1,6 +1,8 @@
 error[E0308]: mismatched types
   --> $DIR/fully-qualified-type-name4.rs:6:12
    |
+LL | fn bar(x: usize) -> Option<usize> {
+   |                     ------------- expected `std::option::Option<usize>` because of return type
 LL |     return x;
    |            ^ expected enum `std::option::Option`, found usize
    |

src/test/ui/liveness/liveness-forgot-ret.stderr

@@ -2,7 +2,7 @@ error[E0308]: mismatched types
   --> $DIR/liveness-forgot-ret.rs:3:19
    |
 LL | fn f(a: isize) -> isize { if god_exists(a) { return 5; }; }
-   |    -              ^^^^^ expected isize, found ()    - expected because of this statement
+   |    -              ^^^^^ expected isize, found ()
    |    |
    |    this function's body doesn't return
    |

src/test/ui/point-to-type-err-cause-on-impl-trait-return-2.rs

@@ -0,0 +1,17 @@
+fn unrelated() -> Result<(), std::string::ParseError> {  // #57664
+    let x = 0;
+
+    match x {
+        1 => {
+            let property_value_as_string = "a".parse()?;
+        }
+        2 => {
+            let value: &bool = unsafe { &42 };
+            //~^ ERROR mismatched types
+        }
+    };
+
+    Ok(())
+}
+
+fn main() {}

src/test/ui/point-to-type-err-cause-on-impl-trait-return-2.stderr

@@ -0,0 +1,12 @@
+error[E0308]: mismatched types
+  --> $DIR/point-to-type-err-cause-on-impl-trait-return-2.rs:9:41
+   |
+LL |             let value: &bool = unsafe { &42 };
+   |                                         ^^^ expected bool, found integer
+   |
+   = note: expected type `&bool`
+              found type `&{integer}`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.

src/test/ui/point-to-type-err-cause-on-impl-trait-return.rs

@@ -0,0 +1,36 @@
+fn foo() -> impl std::fmt::Display {
+    if false {
+        return 0i32;
+    }
+    1u32
+    //~^ ERROR mismatched types
+}
+
+fn bar() -> impl std::fmt::Display {
+    if false {
+        return 0i32;
+    } else {
+        return 1u32;
+        //~^ ERROR mismatched types
+    }
+}
+
+fn baz() -> impl std::fmt::Display {
+    if false {
+    //~^ ERROR mismatched types
+        return 0i32;
+    } else {
+        1u32
+    }
+}
+
+fn qux() -> impl std::fmt::Display {
+    if false {
+        0i32
+    } else {
+        1u32
+        //~^ ERROR if and else have incompatible types
+    }
+}
+
+fn main() {}

src/test/ui/point-to-type-err-cause-on-impl-trait-return.stderr

@@ -0,0 +1,58 @@
+error[E0308]: mismatched types
+  --> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:5:5
+   |
+LL |         return 0i32;
+   |                ---- expected because of this statement
+LL |     }
+LL |     1u32
+   |     ^^^^ expected i32, found u32
+   |
+   = note: expected type `i32`
+              found type `u32`
+
+error[E0308]: mismatched types
+  --> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:13:16
+   |
+LL |         return 0i32;
+   |                ---- expected because of this statement
+LL |     } else {
+LL |         return 1u32;
+   |                ^^^^ expected i32, found u32
+   |
+   = note: expected type `i32`
+              found type `u32`
+
+error[E0308]: mismatched types
+  --> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:19:5
+   |
+LL | /     if false {
+LL | |     //~^ ERROR mismatched types
+LL | |         return 0i32;
+   | |                ---- expected because of this statement
+LL | |     } else {
+LL | |         1u32
+LL | |     }
+   | |_____^ expected i32, found u32
+   |
+   = note: expected type `i32`
+              found type `u32`
+
+error[E0308]: if and else have incompatible types
+  --> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:31:9
+   |
+LL | /     if false {
+LL | |         0i32
+   | |         ---- expected because of this
+LL | |     } else {
+LL | |         1u32
+   | |         ^^^^ expected i32, found u32
+LL | |         //~^ ERROR if and else have incompatible types
+LL | |     }
+   | |_____- if and else have incompatible types
+   |
+   = note: expected type `i32`
+              found type `u32`
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0308`.

src/test/ui/proc-macro/span-preservation.stderr

@@ -15,6 +15,9 @@ LL |     let x: usize = "hello";;;;; //~ ERROR mismatched types
 error[E0308]: mismatched types
   --> $DIR/span-preservation.rs:19:29
    |
+LL | fn b(x: Option<isize>) -> usize {
+   |                           ----- expected `usize` because of return type
+LL |     match x {
 LL |         Some(x) => { return x }, //~ ERROR mismatched types
    |                             ^ expected usize, found isize
 

src/test/ui/return/return-from-diverging.stderr

@@ -1,6 +1,8 @@
 error[E0308]: mismatched types
   --> $DIR/return-from-diverging.rs:4:12
    |
+LL | fn fail() -> ! {
+   |              - expected `!` because of return type
 LL |     return "wow"; //~ ERROR mismatched types
    |            ^^^^^ expected !, found reference
    |

src/test/ui/tail-typeck.stderr

@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/tail-typeck.rs:3:26
    |
 LL | fn f() -> isize { return g(); }
-   |                          ^^^ expected isize, found usize
+   |           -----          ^^^ expected isize, found usize
+   |           |
+   |           expected `isize` because of return type
 
 error: aborting due to previous error
 

src/test/ui/wrong-ret-type.stderr

@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/wrong-ret-type.rs:2:49
    |
 LL | fn mk_int() -> usize { let i: isize = 3; return i; }
-   |                                                 ^ expected usize, found isize
+   |                -----                            ^ expected usize, found isize
+   |                |
+   |                expected `usize` because of return type
 
 error: aborting due to previous error