will not suggest for postfix operator when can not handle precedences well

Author: chenyukang

compiler/rustc_parse/src/parser/diagnostics.rs

@@ -1316,7 +1316,11 @@ impl<'a> Parser<'a> {
                         self.prefix_inc_dec_suggest(base_src, kind, spans).emit(&mut err)
                     }
                     UnaryFixity::Post => {
-                        self.postfix_inc_dec_suggest(base_src, kind, spans).emit(&mut err)
+                        // won't suggest since we can not handle the precedences
+                        // for example: `a + b++` has been parsed (a + b)++ and we can not suggest here
+                        if !matches!(base.kind, ExprKind::Binary(_, _, _)) {
+                            self.postfix_inc_dec_suggest(base_src, kind, spans).emit(&mut err)
+                        }
                     }
                 }
             }

src/test/ui/parser/issue-104867-inc-dec-2.rs

@@ -16,6 +16,7 @@ fn test3() {
 fn test4() {
     let mut i = 0;
     let _ = i + i++; //~ ERROR Rust has no postfix increment operator
+    // won't suggest since we can not handle the precedences
 }
 
 fn test5() {
@@ -38,4 +39,14 @@ fn test8() {
     let _ = i++ + ++i; //~ ERROR Rust has no postfix increment operator
 }
 
+fn test9() {
+    let mut i = 0;
+    let _ = (1 + 2 + i)++; //~ ERROR Rust has no postfix increment operator
+}
+
+fn test10() {
+    let mut i = 0;
+    let _ = (i++ + 1) + 2; //~ ERROR Rust has no postfix increment operator
+}
+
 fn main() { }

src/test/ui/parser/issue-104867-inc-dec-2.stderr

@@ -36,14 +36,9 @@ error: Rust has no postfix increment operator
    |
 LL |     let _ = i + i++;
    |                  ^^ not a valid postfix operator
-   |
-help: use `+= 1` instead
-   |
-LL |     let _ = { let tmp = i + i; i + i += 1; tmp };
-   |             +++++++++++      ~~~~~~~~~~~~~~~~~~~
 
 error: Rust has no postfix increment operator
-  --> $DIR/issue-104867-inc-dec-2.rs:23:14
+  --> $DIR/issue-104867-inc-dec-2.rs:24:14
    |
 LL |     let _ = i++ + i;
    |              ^^ not a valid postfix operator
@@ -54,7 +49,7 @@ LL |     let _ = { let tmp = i; i += 1; tmp } + i;
    |             +++++++++++  ~~~~~~~~~~~~~~~
 
 error: Rust has no postfix increment operator
-  --> $DIR/issue-104867-inc-dec-2.rs:28:14
+  --> $DIR/issue-104867-inc-dec-2.rs:29:14
    |
 LL |     let _ = i++ + i++;
    |              ^^ not a valid postfix operator
@@ -65,7 +60,7 @@ LL |     let _ = { let tmp = i; i += 1; tmp } + i++;
    |             +++++++++++  ~~~~~~~~~~~~~~~
 
 error: Rust has no prefix increment operator
-  --> $DIR/issue-104867-inc-dec-2.rs:33:13
+  --> $DIR/issue-104867-inc-dec-2.rs:34:13
    |
 LL |     let _ = ++i + i++;
    |             ^^ not a valid prefix operator
@@ -76,7 +71,7 @@ LL |     let _ = { i += 1; i } + i++;
    |             ~   +++++++++
 
 error: Rust has no postfix increment operator
-  --> $DIR/issue-104867-inc-dec-2.rs:38:14
+  --> $DIR/issue-104867-inc-dec-2.rs:39:14
    |
 LL |     let _ = i++ + ++i;
    |              ^^ not a valid postfix operator
@@ -86,5 +81,27 @@ help: use `+= 1` instead
 LL |     let _ = { let tmp = i; i += 1; tmp } + ++i;
    |             +++++++++++  ~~~~~~~~~~~~~~~
 
-error: aborting due to 8 previous errors
+error: Rust has no postfix increment operator
+  --> $DIR/issue-104867-inc-dec-2.rs:44:24
+   |
+LL |     let _ = (1 + 2 + i)++;
+   |                        ^^ not a valid postfix operator
+   |
+help: use `+= 1` instead
+   |
+LL |     let _ = { let tmp = (1 + 2 + i); (1 + 2 + i) += 1; tmp };
+   |             +++++++++++            ~~~~~~~~~~~~~~~~~~~~~~~~~
+
+error: Rust has no postfix increment operator
+  --> $DIR/issue-104867-inc-dec-2.rs:49:15
+   |
+LL |     let _ = (i++ + 1) + 2;
+   |               ^^ not a valid postfix operator
+   |
+help: use `+= 1` instead
+   |
+LL |     let _ = ({ let tmp = i; i += 1; tmp } + 1) + 2;
+   |              +++++++++++  ~~~~~~~~~~~~~~~
+
+error: aborting due to 10 previous errors