Merge pull request #18908 from jnyfah/error-braces

Fix: Detect missing errors for } braces before else in let...else statements
rust-lang · Jan 17, 2025 · cd199ea · cd199ea
2 parents 903bc81 + 31c07e4
commit cd199ea
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Showing 23 changed files with 637 additions and 12 deletions.
diff --git a/crates/parser/src/event.rs b/crates/parser/src/event.rs
@@ -12,7 +12,7 @@ use crate::{
 /// `Parser` produces a flat list of `Event`s.
 /// They are converted to a tree-structure in
 /// a separate pass, via `TreeBuilder`.
-#[derive(Debug)]
+#[derive(Debug, PartialEq)]
 pub(crate) enum Event {
     /// This event signifies the start of the node.
     /// It should be either abandoned (in which case the

diff --git a/crates/parser/src/grammar/expressions.rs b/crates/parser/src/grammar/expressions.rs
@@ -134,10 +134,12 @@ pub(super) fn let_stmt(p: &mut Parser<'_>, with_semi: Semicolon) {
         // test_err let_else_right_curly_brace
         // fn func() { let Some(_) = {Some(1)} else { panic!("h") };}
         if let Some(expr) = expr_after_eq {
-            if BlockLike::is_blocklike(expr.kind()) {
-                p.error(
-                    "right curly brace `}` before `else` in a `let...else` statement not allowed",
-                )
+            if let Some(token) = expr.last_token(p) {
+                if token == T!['}'] {
+                    p.error(
+                        "right curly brace `}` before `else` in a `let...else` statement not allowed"
+                    )
+                }
             }
         }
 

diff --git a/crates/parser/src/parser.rs b/crates/parser/src/parser.rs
@@ -318,7 +318,8 @@ impl Marker {
             _ => unreachable!(),
         }
         p.push_event(Event::Finish);
-        CompletedMarker::new(self.pos, kind)
+        let end_pos = p.events.len() as u32;
+        CompletedMarker::new(self.pos, end_pos, kind)
     }
 
     /// Abandons the syntax tree node. All its children
@@ -336,13 +337,14 @@ impl Marker {
 }
 
 pub(crate) struct CompletedMarker {
-    pos: u32,
+    start_pos: u32,
+    end_pos: u32,
     kind: SyntaxKind,
 }
 
 impl CompletedMarker {
-    fn new(pos: u32, kind: SyntaxKind) -> Self {
-        CompletedMarker { pos, kind }
+    fn new(start_pos: u32, end_pos: u32, kind: SyntaxKind) -> Self {
+        CompletedMarker { start_pos, end_pos, kind }
     }
 
     /// This method allows to create a new node which starts
@@ -360,10 +362,10 @@ impl CompletedMarker {
     /// distance to `NEWSTART` into forward_parent(=2 in this case);
     pub(crate) fn precede(self, p: &mut Parser<'_>) -> Marker {
         let new_pos = p.start();
-        let idx = self.pos as usize;
+        let idx = self.start_pos as usize;
         match &mut p.events[idx] {
             Event::Start { forward_parent, .. } => {
-                *forward_parent = Some(new_pos.pos - self.pos);
+                *forward_parent = Some(new_pos.pos - self.start_pos);
             }
             _ => unreachable!(),
         }
@@ -376,7 +378,7 @@ impl CompletedMarker {
         let idx = m.pos as usize;
         match &mut p.events[idx] {
             Event::Start { forward_parent, .. } => {
-                *forward_parent = Some(self.pos - m.pos);
+                *forward_parent = Some(self.start_pos - m.pos);
             }
             _ => unreachable!(),
         }
@@ -386,4 +388,13 @@ impl CompletedMarker {
     pub(crate) fn kind(&self) -> SyntaxKind {
         self.kind
     }
+
+    pub(crate) fn last_token(&self, p: &Parser<'_>) -> Option<SyntaxKind> {
+        let end_pos = self.end_pos as usize;
+        debug_assert_eq!(p.events[end_pos - 1], Event::Finish);
+        p.events[..end_pos].iter().rev().find_map(|event| match event {
+            Event::Token { kind, .. } => Some(*kind),
+            _ => None,
+        })
+    }
 }
diff --git a/crates/parser/test_data/parser/err/0056_let_else_right_curly_brace_struct.rast b/crates/parser/test_data/parser/err/0056_let_else_right_curly_brace_struct.rast
@@ -0,0 +1,79 @@
+SOURCE_FILE
+  STRUCT
+    STRUCT_KW "struct"
+    WHITESPACE " "
+    NAME
+      IDENT "X"
+    WHITESPACE " "
+    RECORD_FIELD_LIST
+      L_CURLY "{"
+      RECORD_FIELD
+        NAME
+          IDENT "a"
+        COLON ":"
+        WHITESPACE " "
+        PATH_TYPE
+          PATH
+            PATH_SEGMENT
+              NAME_REF
+                IDENT "i32"
+      R_CURLY "}"
+  WHITESPACE "\n"
+  FN
+    FN_KW "fn"
+    WHITESPACE " "
+    NAME
+      IDENT "f"
+    PARAM_LIST
+      L_PAREN "("
+      R_PAREN ")"
+    WHITESPACE " "
+    BLOCK_EXPR
+      STMT_LIST
+        L_CURLY "{"
+        WHITESPACE "\n    "
+        LET_STMT
+          LET_KW "let"
+          WHITESPACE " "
+          IDENT_PAT
+            NAME
+              IDENT "foo"
+          WHITESPACE " "
+          EQ "="
+          WHITESPACE " "
+          RECORD_EXPR
+            PATH
+              PATH_SEGMENT
+                NAME_REF
+                  IDENT "X"
+            WHITESPACE " "
+            RECORD_EXPR_FIELD_LIST
+              L_CURLY "{"
+              WHITESPACE "\n        "
+              RECORD_EXPR_FIELD
+                NAME_REF
+                  IDENT "a"
+                COLON ":"
+                WHITESPACE " "
+                LITERAL
+                  INT_NUMBER "1"
+              WHITESPACE "\n    "
+              R_CURLY "}"
+          WHITESPACE " "
+          LET_ELSE
+            ELSE_KW "else"
+            WHITESPACE " "
+            BLOCK_EXPR
+              STMT_LIST
+                L_CURLY "{"
+                WHITESPACE "\n        "
+                EXPR_STMT
+                  RETURN_EXPR
+                    RETURN_KW "return"
+                  SEMICOLON ";"
+                WHITESPACE "\n    "
+                R_CURLY "}"
+          SEMICOLON ";"
+        WHITESPACE "\n"
+        R_CURLY "}"
+error 63: right curly brace `}` before `else` in a `let...else` statement not allowed
diff --git a/crates/parser/test_data/parser/err/0056_let_else_right_curly_brace_struct.rs b/crates/parser/test_data/parser/err/0056_let_else_right_curly_brace_struct.rs
@@ -0,0 +1,8 @@
+struct X {a: i32}
+fn f() {
+    let foo = X {
+        a: 1
+    } else {
+        return;
+    };
+}
diff --git a/crates/parser/test_data/parser/err/0057_let_else_right_curly_brace_arithmetic.rast b/crates/parser/test_data/parser/err/0057_let_else_right_curly_brace_arithmetic.rast
@@ -0,0 +1,42 @@
+SOURCE_FILE
+  ERROR
+    LET_KW "let"
+    WHITESPACE " "
+    IDENT_PAT
+      NAME
+        IDENT "foo"
+    WHITESPACE " "
+    EQ "="
+    WHITESPACE " "
+    BIN_EXPR
+      LITERAL
+        INT_NUMBER "1"
+      WHITESPACE " "
+      PLUS "+"
+      WHITESPACE " "
+      BLOCK_EXPR
+        STMT_LIST
+          L_CURLY "{"
+          WHITESPACE "\n    "
+          LITERAL
+            INT_NUMBER "1"
+          WHITESPACE "\n"
+          R_CURLY "}"
+    WHITESPACE " "
+    LET_ELSE
+      ELSE_KW "else"
+      WHITESPACE " "
+      BLOCK_EXPR
+        STMT_LIST
+          L_CURLY "{"
+          WHITESPACE "\n    "
+          EXPR_STMT
+            RETURN_EXPR
+              RETURN_KW "return"
+            SEMICOLON ";"
+          WHITESPACE "\n"
+          R_CURLY "}"
+    SEMICOLON ";"
+  WHITESPACE "\n"
+error 0: expected an item
+error 23: right curly brace `}` before `else` in a `let...else` statement not allowed
diff --git a/crates/parser/test_data/parser/err/0057_let_else_right_curly_brace_arithmetic.rs b/crates/parser/test_data/parser/err/0057_let_else_right_curly_brace_arithmetic.rs
@@ -0,0 +1,5 @@
+let foo = 1 + {
+    1
+} else {
+    return;
+};
diff --git a/crates/parser/test_data/parser/err/0057_let_else_right_curly_brace_format_args.rast b/crates/parser/test_data/parser/err/0057_let_else_right_curly_brace_format_args.rast
@@ -0,0 +1,90 @@
+SOURCE_FILE
+  FN
+    FN_KW "fn"
+    WHITESPACE " "
+    NAME
+      IDENT "r"
+    PARAM_LIST
+      L_PAREN "("
+      R_PAREN ")"
+    WHITESPACE " "
+    BLOCK_EXPR
+      STMT_LIST
+        L_CURLY "{"
+        WHITESPACE "\n    "
+        LET_STMT
+          LET_KW "let"
+          WHITESPACE " "
+          IDENT_PAT
+            NAME
+              IDENT "ok"
+          WHITESPACE " "
+          EQ "="
+          WHITESPACE " "
+          MACRO_EXPR
+            MACRO_CALL
+              PATH
+                PATH_SEGMENT
+                  NAME_REF
+                    IDENT "format_args"
+              BANG "!"
+              TOKEN_TREE
+                L_PAREN "("
+                STRING "\"\""
+                R_PAREN ")"
+          WHITESPACE " "
+          LET_ELSE
+            ELSE_KW "else"
+            WHITESPACE " "
+            BLOCK_EXPR
+              STMT_LIST
+                L_CURLY "{"
+                WHITESPACE " "
+                EXPR_STMT
+                  RETURN_EXPR
+                    RETURN_KW "return"
+                  SEMICOLON ";"
+                WHITESPACE " "
+                R_CURLY "}"
+          SEMICOLON ";"
+        WHITESPACE "\n\n    "
+        LET_STMT
+          LET_KW "let"
+          WHITESPACE " "
+          IDENT_PAT
+            NAME
+              IDENT "bad"
+          WHITESPACE " "
+          EQ "="
+          WHITESPACE " "
+          MACRO_EXPR
+            MACRO_CALL
+              PATH
+                PATH_SEGMENT
+                  NAME_REF
+                    IDENT "format_args"
+              BANG "!"
+              WHITESPACE " "
+              TOKEN_TREE
+                L_CURLY "{"
+                STRING "\"\""
+                R_CURLY "}"
+          WHITESPACE " "
+          LET_ELSE
+            ELSE_KW "else"
+            WHITESPACE " "
+            BLOCK_EXPR
+              STMT_LIST
+                L_CURLY "{"
+                WHITESPACE " "
+                EXPR_STMT
+                  RETURN_EXPR
+                    RETURN_KW "return"
+                  SEMICOLON ";"
+                WHITESPACE " "
+                R_CURLY "}"
+          SEMICOLON ";"
+        WHITESPACE "\n"
+        R_CURLY "}"
+  WHITESPACE "\n"
+error 89: right curly brace `}` before `else` in a `let...else` statement not allowed
diff --git a/crates/parser/test_data/parser/err/0057_let_else_right_curly_brace_format_args.rs b/crates/parser/test_data/parser/err/0057_let_else_right_curly_brace_format_args.rs
@@ -0,0 +1,5 @@
+fn r() {
+    let ok = format_args!("") else { return; };
+
+    let bad = format_args! {""} else { return; };
+}
diff --git a/crates/parser/test_data/parser/err/0058_let_else_right_curly_brace_range.rast b/crates/parser/test_data/parser/err/0058_let_else_right_curly_brace_range.rast
@@ -0,0 +1,40 @@
+SOURCE_FILE
+  ERROR
+    LET_KW "let"
+    WHITESPACE " "
+    IDENT_PAT
+      NAME
+        IDENT "foo"
+    WHITESPACE " "
+    EQ "="
+    WHITESPACE " "
+    RANGE_EXPR
+      LITERAL
+        INT_NUMBER "1"
+      DOT2 ".."
+      BLOCK_EXPR
+        STMT_LIST
+          L_CURLY "{"
+          WHITESPACE "\n    "
+          LITERAL
+            INT_NUMBER "1"
+          WHITESPACE "\n"
+          R_CURLY "}"
+    WHITESPACE " "
+    LET_ELSE
+      ELSE_KW "else"
+      WHITESPACE " "
+      BLOCK_EXPR
+        STMT_LIST
+          L_CURLY "{"
+          WHITESPACE "\n    "
+          EXPR_STMT
+            RETURN_EXPR
+              RETURN_KW "return"
+            SEMICOLON ";"
+          WHITESPACE "\n"
+          R_CURLY "}"
+    SEMICOLON ";"
+  WHITESPACE "\n"
+error 0: expected an item
+error 22: right curly brace `}` before `else` in a `let...else` statement not allowed
diff --git a/crates/parser/test_data/parser/err/0058_let_else_right_curly_brace_range.rs b/crates/parser/test_data/parser/err/0058_let_else_right_curly_brace_range.rs
@@ -0,0 +1,5 @@
+let foo = 1..{
+    1
+} else {
+    return;
+};