Use expr parse restrictions for let expr parsing

src/test/ui/rfc-2294-if-let-guard/feature-gate.rs

@@ -32,6 +32,8 @@ fn _if_let_guard() {
         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
         //~^ ERROR `if let` guards are experimental
         //~| ERROR expected expression, found `let` statement
+        //~| ERROR expected expression, found `let` statement
+        //~| ERROR expected expression, found `let` statement
 
         () if let Range { start: _, end: _ } = (true..true) && false => {}
         //~^ ERROR `if let` guards are experimental

src/test/ui/rfc-2294-if-let-guard/feature-gate.stderr

@@ -41,19 +41,31 @@ LL |         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 =
    |                                          ^^^
 
 error: expected expression, found `let` statement
-  --> $DIR/feature-gate.rs:52:16
+  --> $DIR/feature-gate.rs:32:55
+   |
+LL |         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
+   |                                                       ^^^
+
+error: expected expression, found `let` statement
+  --> $DIR/feature-gate.rs:32:68
+   |
+LL |         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
+   |                                                                    ^^^
+
+error: expected expression, found `let` statement
+  --> $DIR/feature-gate.rs:54:16
    |
 LL |     use_expr!((let 0 = 1 && 0 == 0));
    |                ^^^
 
 error: expected expression, found `let` statement
-  --> $DIR/feature-gate.rs:54:16
+  --> $DIR/feature-gate.rs:56:16
    |
 LL |     use_expr!((let 0 = 1));
    |                ^^^
 
 error: no rules expected the token `let`
-  --> $DIR/feature-gate.rs:62:15
+  --> $DIR/feature-gate.rs:64:15
    |
 LL |     macro_rules! use_expr {
    |     --------------------- when calling this macro
@@ -102,7 +114,7 @@ LL |         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 =
    = help: you can write `if matches!(<expr>, <pattern>)` instead of `if let <pattern> = <expr>`
 
 error[E0658]: `if let` guards are experimental
-  --> $DIR/feature-gate.rs:36:12
+  --> $DIR/feature-gate.rs:38:12
    |
 LL |         () if let Range { start: _, end: _ } = (true..true) && false => {}
    |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -112,7 +124,7 @@ LL |         () if let Range { start: _, end: _ } = (true..true) && false => {}
    = help: you can write `if matches!(<expr>, <pattern>)` instead of `if let <pattern> = <expr>`
 
 error[E0658]: `if let` guards are experimental
-  --> $DIR/feature-gate.rs:58:12
+  --> $DIR/feature-gate.rs:60:12
    |
 LL |         () if let 0 = 1 => {}
    |            ^^^^^^^^^^^^
@@ -121,6 +133,6 @@ LL |         () if let 0 = 1 => {}
    = help: add `#![feature(if_let_guard)]` to the crate attributes to enable
    = help: you can write `if matches!(<expr>, <pattern>)` instead of `if let <pattern> = <expr>`
 
-error: aborting due to 16 previous errors
+error: aborting due to 18 previous errors
 
 For more information about this error, try `rustc --explain E0658`.

src/test/ui/rfc-2497-if-let-chains/disallowed-positions.rs

@@ -51,6 +51,8 @@ fn _if() {
     //~| ERROR `let` expressions are not supported here
     //~| ERROR `let` expressions are not supported here
     //~| ERROR expected expression, found `let` statement
+    //~| ERROR expected expression, found `let` statement
+    //~| ERROR expected expression, found `let` statement
 }
 
 fn _while() {
@@ -81,6 +83,8 @@ fn _while() {
     //~| ERROR `let` expressions are not supported here
     //~| ERROR `let` expressions are not supported here
     //~| ERROR expected expression, found `let` statement
+    //~| ERROR expected expression, found `let` statement
+    //~| ERROR expected expression, found `let` statement
 }
 
 fn _macros() {
@@ -146,6 +150,7 @@ fn nested_within_if_expr() {
     //~| ERROR expected expression, found `let` statement
     if true || (true && let 0 = 0) {}
     //~^ ERROR `let` expressions are not supported here
+    //~| ERROR expected expression, found `let` statement
 
     let mut x = true;
     if x = let 0 = 0 {}
@@ -237,6 +242,7 @@ fn nested_within_while_expr() {
     //~| ERROR expected expression, found `let` statement
     while true || (true && let 0 = 0) {}
     //~^ ERROR `let` expressions are not supported here
+    //~| ERROR expected expression, found `let` statement
 
     let mut x = true;
     while x = let 0 = 0 {}
@@ -388,16 +394,19 @@ fn inside_const_generic_arguments() {
     if let A::<{
         true && let 1 = 1
         //~^ ERROR `let` expressions are not supported here
+        //~| ERROR expected expression, found `let` statement
     }>::O = 5 {}
 
     while let A::<{
         true && let 1 = 1
         //~^ ERROR `let` expressions are not supported here
+        //~| ERROR expected expression, found `let` statement
     }>::O = 5 {}
 
     if A::<{
         true && let 1 = 1
         //~^ ERROR `let` expressions are not supported here
+        //~| ERROR expected expression, found `let` statement
     }>::O == 5 {}
 
     // In the cases above we have `ExprKind::Block` to help us out.
@@ -409,7 +418,8 @@ fn inside_const_generic_arguments() {
     if A::<
         true && let 1 = 1
         //~^ ERROR `let` expressions are not supported here
-        //~| ERROR  expressions must be enclosed in braces
+        //~| ERROR expressions must be enclosed in braces
+        //~| ERROR expected expression, found `let` statement
     >::O == 5 {}
 }