Auto merge of #103636 - chenyukang:yukang/fix-103587-sugg-if-let, r=jackh276,davidtwco

Recover from common if let syntax mistakes/typos

Fixes #103587

src/test/ui/did_you_mean/issue-103909.stderr

@@ -14,6 +14,11 @@ error[E0308]: mismatched types
    |
 LL |     if Err(err) = File::open("hello.txt") {
    |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `bool`, found `()`
+   |
+help: consider adding `let`
+   |
+LL |     if let Err(err) = File::open("hello.txt") {
+   |        +++
 
 error: aborting due to 2 previous errors
 

src/test/ui/inference/issue-103587.rs

@@ -0,0 +1,12 @@
+fn main() {
+    let x = Some(123);
+
+    if let Some(_) == x {}
+    //~^ ERROR expected `=`, found `==`
+
+    if Some(_) = x {}
+    //~^ ERROR mismatched types
+
+    if None = x { }
+    //~^ ERROR mismatched types
+}

src/test/ui/inference/issue-103587.stderr

@@ -0,0 +1,40 @@
+error: expected `=`, found `==`
+  --> $DIR/issue-103587.rs:4:20
+   |
+LL |     if let Some(_) == x {}
+   |                    ^^
+   |
+help: consider using `=` here
+   |
+LL |     if let Some(_) = x {}
+   |                    ~
+
+error[E0308]: mismatched types
+  --> $DIR/issue-103587.rs:7:8
+   |
+LL |     if Some(_) = x {}
+   |        ^^^^^^^^^^^ expected `bool`, found `()`
+   |
+help: consider adding `let`
+   |
+LL |     if let Some(_) = x {}
+   |        +++
+
+error[E0308]: mismatched types
+  --> $DIR/issue-103587.rs:10:8
+   |
+LL |     if None = x { }
+   |        ^^^^^^^^ expected `bool`, found `()`
+   |
+help: you might have meant to use pattern matching
+   |
+LL |     if let None = x { }
+   |        +++
+help: you might have meant to compare for equality
+   |
+LL |     if None == x { }
+   |              +
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0308`.

src/test/ui/suggestions/if-let-typo.stderr

@@ -25,12 +25,22 @@ error[E0308]: mismatched types
    |
 LL |     if Some(x) = foo {}
    |        ^^^^^^^^^^^^^ expected `bool`, found `()`
+   |
+help: consider adding `let`
+   |
+LL |     if let Some(x) = foo {}
+   |        +++
 
 error[E0308]: mismatched types
   --> $DIR/if-let-typo.rs:6:8
    |
 LL |     if Some(foo) = bar {}
    |        ^^^^^^^^^^^^^^^ expected `bool`, found `()`
+   |
+help: consider adding `let`
+   |
+LL |     if let Some(foo) = bar {}
+   |        +++
 
 error[E0308]: mismatched types
   --> $DIR/if-let-typo.rs:7:8
@@ -51,6 +61,11 @@ error[E0308]: mismatched types
    |
 LL |     if Some(3) = foo {}
    |        ^^^^^^^^^^^^^ expected `bool`, found `()`
+   |
+help: consider adding `let`
+   |
+LL |     if let Some(3) = foo {}
+   |        +++
 
 error: aborting due to 7 previous errors
 

src/tools/clippy/tests/ui/crashes/ice-6250.stderr

@@ -23,6 +23,11 @@ error[E0308]: mismatched types
    |
 LL |         Some(reference) = cache.data.get(key) {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `bool`, found `()`
+   |
+help: consider adding `let`
+   |
+LL |         let Some(reference) = cache.data.get(key) {
+   |         +++
 
 error: aborting due to 3 previous errors