add test for assignment x = y where type bool is expected.

Author: Centril

src/test/ui/type/type-check/assignment-expected-bool.rs

@@ -0,0 +1,29 @@
+// The purpose of this text is to ensure that we get good
+// diagnostics when a `bool` is expected but that due to
+// an assignment expression `x = y` the type is `()`.
+
+fn main() {
+    let _: bool = 0 = 0; //~ ERROR mismatched types [E0308]
+
+    let _: bool = match 0 {
+        0 => 0 = 0, //~ ERROR mismatched types [E0308]
+        _ => 0 = 0, //~ ERROR mismatched types [E0308]
+    };
+
+    let _: bool = match true {
+        true => 0 = 0, //~ ERROR mismatched types [E0308]
+        _ => (),
+    };
+
+    if 0 = 0 {} //~ ERROR mismatched types [E0308]
+
+    let _: bool = if { 0 = 0 } { //~ ERROR mismatched types [E0308]
+        0 = 0 //~ ERROR mismatched types [E0308]
+    } else {
+        0 = 0 //~ ERROR mismatched types [E0308]
+    };
+
+    let _ = (0 = 0) //~ ERROR mismatched types [E0308]
+        && { 0 = 0 } //~ ERROR mismatched types [E0308]
+        || (0 = 0); //~ ERROR mismatched types [E0308]
+}

src/test/ui/type/type-check/assignment-expected-bool.stderr

@@ -0,0 +1,135 @@
+error[E0308]: mismatched types
+  --> $DIR/assignment-expected-bool.rs:6:19
+   |
+LL |     let _: bool = 0 = 0;
+   |                   ^^^^^
+   |                   |
+   |                   expected bool, found ()
+   |                   help: try comparing for equality: `0 == 0`
+   |
+   = note: expected type `bool`
+              found type `()`
+
+error[E0308]: mismatched types
+  --> $DIR/assignment-expected-bool.rs:9:14
+   |
+LL |         0 => 0 = 0,
+   |              ^^^^^
+   |              |
+   |              expected bool, found ()
+   |              help: try comparing for equality: `0 == 0`
+   |
+   = note: expected type `bool`
+              found type `()`
+
+error[E0308]: mismatched types
+  --> $DIR/assignment-expected-bool.rs:10:14
+   |
+LL |         _ => 0 = 0,
+   |              ^^^^^
+   |              |
+   |              expected bool, found ()
+   |              help: try comparing for equality: `0 == 0`
+   |
+   = note: expected type `bool`
+              found type `()`
+
+error[E0308]: mismatched types
+  --> $DIR/assignment-expected-bool.rs:14:17
+   |
+LL |         true => 0 = 0,
+   |                 ^^^^^
+   |                 |
+   |                 expected bool, found ()
+   |                 help: try comparing for equality: `0 == 0`
+   |
+   = note: expected type `bool`
+              found type `()`
+
+error[E0308]: mismatched types
+  --> $DIR/assignment-expected-bool.rs:18:8
+   |
+LL |     if 0 = 0 {}
+   |        ^^^^^
+   |        |
+   |        expected bool, found ()
+   |        help: try comparing for equality: `0 == 0`
+   |
+   = note: expected type `bool`
+              found type `()`
+
+error[E0308]: mismatched types
+  --> $DIR/assignment-expected-bool.rs:20:24
+   |
+LL |     let _: bool = if { 0 = 0 } {
+   |                        ^^^^^
+   |                        |
+   |                        expected bool, found ()
+   |                        help: try comparing for equality: `0 == 0`
+   |
+   = note: expected type `bool`
+              found type `()`
+
+error[E0308]: mismatched types
+  --> $DIR/assignment-expected-bool.rs:21:9
+   |
+LL |         0 = 0
+   |         ^^^^^
+   |         |
+   |         expected bool, found ()
+   |         help: try comparing for equality: `0 == 0`
+   |
+   = note: expected type `bool`
+              found type `()`
+
+error[E0308]: mismatched types
+  --> $DIR/assignment-expected-bool.rs:23:9
+   |
+LL |         0 = 0
+   |         ^^^^^
+   |         |
+   |         expected bool, found ()
+   |         help: try comparing for equality: `0 == 0`
+   |
+   = note: expected type `bool`
+              found type `()`
+
+error[E0308]: mismatched types
+  --> $DIR/assignment-expected-bool.rs:26:13
+   |
+LL |     let _ = (0 = 0)
+   |             ^^^^^^^
+   |             |
+   |             expected bool, found ()
+   |             help: try comparing for equality: `0 == 0`
+   |
+   = note: expected type `bool`
+              found type `()`
+
+error[E0308]: mismatched types
+  --> $DIR/assignment-expected-bool.rs:27:14
+   |
+LL |         && { 0 = 0 }
+   |              ^^^^^
+   |              |
+   |              expected bool, found ()
+   |              help: try comparing for equality: `0 == 0`
+   |
+   = note: expected type `bool`
+              found type `()`
+
+error[E0308]: mismatched types
+  --> $DIR/assignment-expected-bool.rs:28:12
+   |
+LL |         || (0 = 0);
+   |            ^^^^^^^
+   |            |
+   |            expected bool, found ()
+   |            help: try comparing for equality: `0 == 0`
+   |
+   = note: expected type `bool`
+              found type `()`
+
+error: aborting due to 11 previous errors
+
+For more information about this error, try `rustc --explain E0308`.