fix #104867, Properly handle postfix inc/dec in standalone and subexpr scenarios

compiler/rustc_parse/src/parser/diagnostics.rs

@@ -159,8 +159,6 @@ enum IsStandalone {
     Standalone,
     /// It's a subexpression, i.e., *not* standalone.
     Subexpr,
-    /// It's maybe standalone; we're not sure.
-    Maybe,
 }
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
@@ -213,14 +211,8 @@ impl MultiSugg {
         err.multipart_suggestion(&self.msg, self.patches, self.applicability);
     }
 
-    /// Overrides individual messages and applicabilities.
-    fn emit_many(
-        err: &mut Diagnostic,
-        msg: &str,
-        applicability: Applicability,
-        suggestions: impl Iterator<Item = Self>,
-    ) {
-        err.multipart_suggestions(msg, suggestions.map(|s| s.patches), applicability);
+    fn emit_verbose(self, err: &mut Diagnostic) {
+        err.multipart_suggestion_verbose(&self.msg, self.patches, self.applicability);
     }
 }
 
@@ -1272,7 +1264,6 @@ impl<'a> Parser<'a> {
         let standalone =
             if prev_is_semi { IsStandalone::Standalone } else { IsStandalone::Subexpr };
         let kind = IncDecRecovery { standalone, op: IncOrDec::Inc, fixity: UnaryFixity::Pre };
-
         self.recover_from_inc_dec(operand_expr, kind, op_span)
     }
 
@@ -1280,13 +1271,13 @@ impl<'a> Parser<'a> {
         &mut self,
         operand_expr: P<Expr>,
         op_span: Span,
+        prev_is_semi: bool,
     ) -> PResult<'a, P<Expr>> {
         let kind = IncDecRecovery {
-            standalone: IsStandalone::Maybe,
+            standalone: if prev_is_semi { IsStandalone::Standalone } else { IsStandalone::Subexpr },
             op: IncOrDec::Inc,
             fixity: UnaryFixity::Post,
         };
-
         self.recover_from_inc_dec(operand_expr, kind, op_span)
     }
 
@@ -1314,35 +1305,20 @@ impl<'a> Parser<'a> {
             UnaryFixity::Post => (base.span.shrink_to_lo(), op_span),
         };
 
+        let Ok(base_src) = self.span_to_snippet(base.span)
+        else { return help_base_case(err, base) };
         match kind.standalone {
-            IsStandalone::Standalone => self.inc_dec_standalone_suggest(kind, spans).emit(&mut err),
-            IsStandalone::Subexpr => {
-                let Ok(base_src) = self.span_to_snippet(base.span)
-                    else { return help_base_case(err, base) };
-                match kind.fixity {
-                    UnaryFixity::Pre => {
-                        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)
-                    }
+            IsStandalone::Standalone => {
+                self.inc_dec_standalone_suggest(kind, spans).emit_verbose(&mut err)
+            }
+            IsStandalone::Subexpr => match kind.fixity {
+                UnaryFixity::Pre => {
+                    self.prefix_inc_dec_suggest(base_src, kind, spans).emit(&mut err)
                 }
-            }
-            IsStandalone::Maybe => {
-                let Ok(base_src) = self.span_to_snippet(base.span)
-                    else { return help_base_case(err, base) };
-                let sugg1 = match kind.fixity {
-                    UnaryFixity::Pre => self.prefix_inc_dec_suggest(base_src, kind, spans),
-                    UnaryFixity::Post => self.postfix_inc_dec_suggest(base_src, kind, spans),
-                };
-                let sugg2 = self.inc_dec_standalone_suggest(kind, spans);
-                MultiSugg::emit_many(
-                    &mut err,
-                    "use `+= 1` instead",
-                    Applicability::Unspecified,
-                    [sugg1, sugg2].into_iter(),
-                )
-            }
+                UnaryFixity::Post => {
+                    self.postfix_inc_dec_suggest(base_src, kind, spans).emit(&mut err)
+                }
+            },
         }
         Err(err)
     }
@@ -1392,7 +1368,6 @@ impl<'a> Parser<'a> {
         }
 
         patches.push((post_span, format!(" {}= 1", kind.op.chr())));
-
         MultiSugg {
             msg: format!("use `{}= 1` instead", kind.op.chr()),
             patches,

compiler/rustc_parse/src/parser/expr.rs

@@ -292,7 +292,15 @@ impl<'a> Parser<'a> {
                 let op_span = self.prev_token.span.to(self.token.span);
                 // Eat the second `+`
                 self.bump();
-                lhs = self.recover_from_postfix_increment(lhs, op_span)?;
+                let prev_is_semi = {
+                    if let Ok(prev_code) = self.sess.source_map().span_to_prev_source(lhs.span) &&
+                          prev_code.trim_end().ends_with(";") {
+                            true
+                    } else {
+                        false
+                    }
+                };
+                lhs = self.recover_from_postfix_increment(lhs, op_span, prev_is_semi)?;
                 continue;
             }
 

src/test/ui/parser/increment-notfixed.fixed

@@ -0,0 +1,63 @@
+// run-rustfix
+
+struct Foo {
+    bar: Bar,
+}
+
+struct Bar {
+    qux: i32,
+}
+
+pub fn post_regular() {
+    let mut i = 0;
+    i += 1; //~ ERROR Rust has no postfix increment operator
+    println!("{}", i);
+}
+
+pub fn post_while() {
+    let mut i = 0;
+    while { let tmp = i; i += 1; tmp } < 5 {
+        //~^ ERROR Rust has no postfix increment operator
+        println!("{}", i);
+    }
+}
+
+pub fn post_regular_tmp() {
+    let mut tmp = 0;
+    tmp += 1; //~ ERROR Rust has no postfix increment operator
+    println!("{}", tmp);
+}
+
+pub fn post_while_tmp() {
+    let mut tmp = 0;
+    while { let tmp_ = tmp; tmp += 1; tmp_ } < 5 {
+        //~^ ERROR Rust has no postfix increment operator
+        println!("{}", tmp);
+    }
+}
+
+pub fn post_field() {
+    let mut foo = Foo { bar: Bar { qux: 0 } };
+    foo.bar.qux += 1;
+    //~^ ERROR Rust has no postfix increment operator
+    println!("{}", foo.bar.qux);
+}
+
+pub fn post_field_tmp() {
+    struct S {
+        tmp: i32
+    }
+    let mut s = S { tmp: 0 };
+    s.tmp += 1;
+    //~^ ERROR Rust has no postfix increment operator
+    println!("{}", s.tmp);
+}
+
+pub fn pre_field() {
+    let mut foo = Foo { bar: Bar { qux: 0 } };
+    foo.bar.qux += 1;
+    //~^ ERROR Rust has no prefix increment operator
+    println!("{}", foo.bar.qux);
+}
+
+fn main() {}

src/test/ui/parser/increment-notfixed.rs

@@ -1,3 +1,5 @@
+// run-rustfix
+
 struct Foo {
     bar: Bar,
 }
@@ -35,7 +37,7 @@ pub fn post_while_tmp() {
 }
 
 pub fn post_field() {
-    let foo = Foo { bar: Bar { qux: 0 } };
+    let mut foo = Foo { bar: Bar { qux: 0 } };
     foo.bar.qux++;
     //~^ ERROR Rust has no postfix increment operator
     println!("{}", foo.bar.qux);
@@ -45,14 +47,14 @@ pub fn post_field_tmp() {
     struct S {
         tmp: i32
     }
-    let s = S { tmp: 0 };
+    let mut s = S { tmp: 0 };
     s.tmp++;
     //~^ ERROR Rust has no postfix increment operator
     println!("{}", s.tmp);
 }
 
 pub fn pre_field() {
-    let foo = Foo { bar: Bar { qux: 0 } };
+    let mut foo = Foo { bar: Bar { qux: 0 } };
     ++foo.bar.qux;
     //~^ ERROR Rust has no prefix increment operator
     println!("{}", foo.bar.qux);

src/test/ui/parser/increment-notfixed.stderr

@@ -1,18 +1,16 @@
 error: Rust has no postfix increment operator
-  --> $DIR/increment-notfixed.rs:11:6
+  --> $DIR/increment-notfixed.rs:13:6
    |
 LL |     i++;
    |      ^^ not a valid postfix operator
    |
 help: use `+= 1` instead
    |
-LL |     { let tmp = i; i += 1; tmp };
-   |     +++++++++++  ~~~~~~~~~~~~~~~
 LL |     i += 1;
    |       ~~~~
 
 error: Rust has no postfix increment operator
-  --> $DIR/increment-notfixed.rs:17:12
+  --> $DIR/increment-notfixed.rs:19:12
    |
 LL |     while i++ < 5 {
    |     -----  ^^ not a valid postfix operator
@@ -23,24 +21,20 @@ help: use `+= 1` instead
    |
 LL |     while { let tmp = i; i += 1; tmp } < 5 {
    |           +++++++++++  ~~~~~~~~~~~~~~~
-LL |     while i += 1 < 5 {
-   |             ~~~~
 
 error: Rust has no postfix increment operator
-  --> $DIR/increment-notfixed.rs:25:8
+  --> $DIR/increment-notfixed.rs:27:8
    |
 LL |     tmp++;
    |        ^^ not a valid postfix operator
    |
 help: use `+= 1` instead
    |
-LL |     { let tmp_ = tmp; tmp += 1; tmp_ };
-   |     ++++++++++++    ~~~~~~~~~~~~~~~~~~
 LL |     tmp += 1;
    |         ~~~~
 
 error: Rust has no postfix increment operator
-  --> $DIR/increment-notfixed.rs:31:14
+  --> $DIR/increment-notfixed.rs:33:14
    |
 LL |     while tmp++ < 5 {
    |     -----    ^^ not a valid postfix operator
@@ -51,37 +45,31 @@ help: use `+= 1` instead
    |
 LL |     while { let tmp_ = tmp; tmp += 1; tmp_ } < 5 {
    |           ++++++++++++    ~~~~~~~~~~~~~~~~~~
-LL |     while tmp += 1 < 5 {
-   |               ~~~~
 
 error: Rust has no postfix increment operator
-  --> $DIR/increment-notfixed.rs:39:16
+  --> $DIR/increment-notfixed.rs:41:16
    |
 LL |     foo.bar.qux++;
    |                ^^ not a valid postfix operator
    |
 help: use `+= 1` instead
    |
-LL |     { let tmp = foo.bar.qux; foo.bar.qux += 1; tmp };
-   |     +++++++++++            ~~~~~~~~~~~~~~~~~~~~~~~~~
 LL |     foo.bar.qux += 1;
    |                 ~~~~
 
 error: Rust has no postfix increment operator
-  --> $DIR/increment-notfixed.rs:49:10
+  --> $DIR/increment-notfixed.rs:51:10
    |
 LL |     s.tmp++;
    |          ^^ not a valid postfix operator
    |
 help: use `+= 1` instead
    |
-LL |     { let tmp = s.tmp; s.tmp += 1; tmp };
-   |     +++++++++++      ~~~~~~~~~~~~~~~~~~~
 LL |     s.tmp += 1;
    |           ~~~~
 
 error: Rust has no prefix increment operator
-  --> $DIR/increment-notfixed.rs:56:5
+  --> $DIR/increment-notfixed.rs:58:5
    |
 LL |     ++foo.bar.qux;
    |     ^^ not a valid prefix operator

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

@@ -0,0 +1,30 @@
+struct S {
+    x: i32,
+}
+
+fn test1() {
+    let mut i = 0;
+    i++; //~ ERROR Rust has no postfix increment operator
+}
+
+fn test2() {
+    let s = S { x: 0 };
+    s.x++; //~ ERROR Rust has no postfix increment operator
+}
+
+fn test3() {
+    let mut i = 0;
+    if i++ == 1 {} //~ ERROR Rust has no postfix increment operator
+}
+
+fn test4() {
+    let mut i = 0;
+    ++i; //~ ERROR Rust has no prefix increment operator
+}
+
+fn test5() {
+    let mut i = 0;
+    if ++i == 1 { } //~ ERROR Rust has no prefix increment operator
+}
+
+fn main() {}

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

@@ -0,0 +1,58 @@
+error: Rust has no postfix increment operator
+  --> $DIR/issue-104867-inc-dec.rs:7:6
+   |
+LL |     i++;
+   |      ^^ not a valid postfix operator
+   |
+help: use `+= 1` instead
+   |
+LL |     i += 1;
+   |       ~~~~
+
+error: Rust has no postfix increment operator
+  --> $DIR/issue-104867-inc-dec.rs:12:8
+   |
+LL |     s.x++;
+   |        ^^ not a valid postfix operator
+   |
+help: use `+= 1` instead
+   |
+LL |     s.x += 1;
+   |         ~~~~
+
+error: Rust has no postfix increment operator
+  --> $DIR/issue-104867-inc-dec.rs:17:9
+   |
+LL |     if i++ == 1 {}
+   |         ^^ not a valid postfix operator
+   |
+help: use `+= 1` instead
+   |
+LL |     if { let tmp = i; i += 1; tmp } == 1 {}
+   |        +++++++++++  ~~~~~~~~~~~~~~~
+
+error: Rust has no prefix increment operator
+  --> $DIR/issue-104867-inc-dec.rs:22:5
+   |
+LL |     ++i;
+   |     ^^ not a valid prefix operator
+   |
+help: use `+= 1` instead
+   |
+LL -     ++i;
+LL +     i += 1;
+   |
+
+error: Rust has no prefix increment operator
+  --> $DIR/issue-104867-inc-dec.rs:27:8
+   |
+LL |     if ++i == 1 { }
+   |        ^^ not a valid prefix operator
+   |
+help: use `+= 1` instead
+   |
+LL |     if { i += 1; i } == 1 { }
+   |        ~   +++++++++
+
+error: aborting due to 5 previous errors
+