Error if assignment after block (#41115)

* Error if assignment after block

* Update src/compiler/diagnosticMessages.json

Co-authored-by: Daniel Rosenwasser <DanielRosenwasser@users.noreply.github.com>

* Fix diags

* Error after block

Co-authored-by: Daniel Rosenwasser <DanielRosenwasser@users.noreply.github.com>
Co-authored-by: Nathan Shively-Sanders <293473+sandersn@users.noreply.github.com>

src/compiler/diagnosticMessages.json

@@ -3308,6 +3308,10 @@
         "category": "Error",
         "code": 2808
     },
+    "Declaration or statement expected. This '=' follows a block of statements, so if you intended to write a destructuring assignment, you might need to wrap the the whole assignment in parentheses.": {
+        "category": "Error",
+        "code": 2809
+    },
 
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",

src/compiler/parser.ts

@@ -2109,8 +2109,7 @@ namespace ts {
 
             while (!isListTerminator(kind)) {
                 if (isListElement(kind, /*inErrorRecovery*/ false)) {
-                    const element = parseListElement(kind, parseElement);
-                    list.push(element);
+                    list.push(parseListElement(kind, parseElement));
 
                     continue;
                 }
@@ -5602,7 +5601,13 @@ namespace ts {
                 const multiLine = scanner.hasPrecedingLineBreak();
                 const statements = parseList(ParsingContext.BlockStatements, parseStatement);
                 parseExpectedMatchingBrackets(SyntaxKind.OpenBraceToken, SyntaxKind.CloseBraceToken, openBracePosition);
-                return finishNode(factory.createBlock(statements, multiLine), pos);
+                const result = finishNode(factory.createBlock(statements, multiLine), pos);
+                if (token() === SyntaxKind.EqualsToken) {
+                    parseErrorAtCurrentToken(Diagnostics.Declaration_or_statement_expected_This_follows_a_block_of_statements_so_if_you_intended_to_write_a_destructuring_assignment_you_might_need_to_wrap_the_the_whole_assignment_in_parentheses);
+                    nextToken();
+                }
+
+                return result;
             }
             else {
                 const statements = createMissingList<Statement>();

tests/baselines/reference/assignmentLHSIsValue.errors.txt

@@ -13,14 +13,15 @@ tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts(2
 tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts(30,1): error TS2364: The left-hand side of an assignment expression must be a variable or a property access.
 tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts(31,1): error TS2364: The left-hand side of an assignment expression must be a variable or a property access.
 tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts(32,1): error TS2364: The left-hand side of an assignment expression must be a variable or a property access.
-tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts(35,9): error TS1128: Declaration or statement expected.
+tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts(35,9): error TS2809: Declaration or statement expected. This '=' follows a block of statements, so if you intended to write a destructuring assignment, you might need to wrap the the whole assignment in parentheses.
 tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts(38,2): error TS2364: The left-hand side of an assignment expression must be a variable or a property access.
 tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts(38,6): error TS2364: The left-hand side of an assignment expression must be a variable or a property access.
 tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts(42,36): error TS1034: 'super' must be followed by an argument list or member access.
 tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts(44,19): error TS1034: 'super' must be followed by an argument list or member access.
 tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts(46,27): error TS1034: 'super' must be followed by an argument list or member access.
-tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts(50,20): error TS1128: Declaration or statement expected.
-tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts(51,11): error TS1005: ';' expected.
+tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts(50,20): error TS2809: Declaration or statement expected. This '=' follows a block of statements, so if you intended to write a destructuring assignment, you might need to wrap the the whole assignment in parentheses.
+tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts(51,11): error TS2809: Declaration or statement expected. This '=' follows a block of statements, so if you intended to write a destructuring assignment, you might need to wrap the the whole assignment in parentheses.
+tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts(51,13): error TS1005: ';' expected.
 tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts(54,1): error TS2364: The left-hand side of an assignment expression must be a variable or a property access.
 tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts(57,1): error TS2364: The left-hand side of an assignment expression must be a variable or a property access.
 tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts(58,2): error TS2631: Cannot assign to 'M' because it is a namespace.
@@ -38,7 +39,7 @@ tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts(6
 tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts(70,1): error TS2364: The left-hand side of an assignment expression must be a variable or a property access.
 
 
-==== tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts (38 errors) ====
+==== tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts (39 errors) ====
     // expected error for all the LHS of assignments
     var value: any;
     
@@ -105,7 +106,7 @@ tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts(7
     // object literals
     { a: 0} = value;
             ~
-!!! error TS1128: Declaration or statement expected.
+!!! error TS2809: Declaration or statement expected. This '=' follows a block of statements, so if you intended to write a destructuring assignment, you might need to wrap the the whole assignment in parentheses.
     
     // array literals
     ['', ''] = value;
@@ -132,9 +133,11 @@ tests/cases/conformance/expressions/assignmentOperator/assignmentLHSIsValue.ts(7
     // function expression
     function bar() { } = value;
                        ~
-!!! error TS1128: Declaration or statement expected.
+!!! error TS2809: Declaration or statement expected. This '=' follows a block of statements, so if you intended to write a destructuring assignment, you might need to wrap the the whole assignment in parentheses.
     () => { } = value;
               ~
+!!! error TS2809: Declaration or statement expected. This '=' follows a block of statements, so if you intended to write a destructuring assignment, you might need to wrap the the whole assignment in parentheses.
+                ~~~~~
 !!! error TS1005: ';' expected.
     
     // function calls

tests/baselines/reference/assignmentLHSIsValue.types

@@ -146,7 +146,7 @@ function bar() { } = value;
 >value : any
 
 () => { } = value;
->() => { } : () => void
+>() => { } = : () => void
 >value : any
 
 // function calls

tests/baselines/reference/destructionAssignmentError.errors.txt

@@ -0,0 +1,27 @@
+tests/cases/compiler/destructionAssignmentError.ts(6,3): error TS2695: Left side of comma operator is unused and has no side effects.
+tests/cases/compiler/destructionAssignmentError.ts(6,10): error TS2809: Declaration or statement expected. This '=' follows a block of statements, so if you intended to write a destructuring assignment, you might need to wrap the the whole assignment in parentheses.
+tests/cases/compiler/destructionAssignmentError.ts(11,3): error TS2695: Left side of comma operator is unused and has no side effects.
+tests/cases/compiler/destructionAssignmentError.ts(12,1): error TS2809: Declaration or statement expected. This '=' follows a block of statements, so if you intended to write a destructuring assignment, you might need to wrap the the whole assignment in parentheses.
+
+
+==== tests/cases/compiler/destructionAssignmentError.ts (4 errors) ====
+    declare function fn(): { a: 1, b: 2 }
+    let a: number;
+    let b: number;
+    
+    ({ a, b } = fn());
+    { a, b } = fn();
+      ~
+!!! error TS2695: Left side of comma operator is unused and has no side effects.
+             ~
+!!! error TS2809: Declaration or statement expected. This '=' follows a block of statements, so if you intended to write a destructuring assignment, you might need to wrap the the whole assignment in parentheses.
+    
+    ({ a, b } =
+    fn());
+    
+    { a, b }
+      ~
+!!! error TS2695: Left side of comma operator is unused and has no side effects.
+    = fn();
+    ~
+!!! error TS2809: Declaration or statement expected. This '=' follows a block of statements, so if you intended to write a destructuring assignment, you might need to wrap the the whole assignment in parentheses.

tests/baselines/reference/destructionAssignmentError.js

@@ -0,0 +1,28 @@
+//// [destructionAssignmentError.ts]
+declare function fn(): { a: 1, b: 2 }
+let a: number;
+let b: number;
+
+({ a, b } = fn());
+{ a, b } = fn();
+
+({ a, b } =
+fn());
+
+{ a, b }
+= fn();
+
+//// [destructionAssignmentError.js]
+var _a, _b;
+var a;
+var b;
+(_a = fn(), a = _a.a, b = _a.b);
+{
+    a, b;
+}
+fn();
+(_b = fn(), a = _b.a, b = _b.b);
+{
+    a, b;
+}
+fn();

tests/baselines/reference/destructionAssignmentError.symbols

@@ -0,0 +1,36 @@
+=== tests/cases/compiler/destructionAssignmentError.ts ===
+declare function fn(): { a: 1, b: 2 }
+>fn : Symbol(fn, Decl(destructionAssignmentError.ts, 0, 0))
+>a : Symbol(a, Decl(destructionAssignmentError.ts, 0, 24))
+>b : Symbol(b, Decl(destructionAssignmentError.ts, 0, 30))
+
+let a: number;
+>a : Symbol(a, Decl(destructionAssignmentError.ts, 1, 3))
+
+let b: number;
+>b : Symbol(b, Decl(destructionAssignmentError.ts, 2, 3))
+
+({ a, b } = fn());
+>a : Symbol(a, Decl(destructionAssignmentError.ts, 4, 2))
+>b : Symbol(b, Decl(destructionAssignmentError.ts, 4, 5))
+>fn : Symbol(fn, Decl(destructionAssignmentError.ts, 0, 0))
+
+{ a, b } = fn();
+>a : Symbol(a, Decl(destructionAssignmentError.ts, 1, 3))
+>b : Symbol(b, Decl(destructionAssignmentError.ts, 2, 3))
+>fn : Symbol(fn, Decl(destructionAssignmentError.ts, 0, 0))
+
+({ a, b } =
+>a : Symbol(a, Decl(destructionAssignmentError.ts, 7, 2))
+>b : Symbol(b, Decl(destructionAssignmentError.ts, 7, 5))
+
+fn());
+>fn : Symbol(fn, Decl(destructionAssignmentError.ts, 0, 0))
+
+{ a, b }
+>a : Symbol(a, Decl(destructionAssignmentError.ts, 1, 3))
+>b : Symbol(b, Decl(destructionAssignmentError.ts, 2, 3))
+
+= fn();
+>fn : Symbol(fn, Decl(destructionAssignmentError.ts, 0, 0))
+

tests/baselines/reference/destructionAssignmentError.types

@@ -0,0 +1,48 @@
+=== tests/cases/compiler/destructionAssignmentError.ts ===
+declare function fn(): { a: 1, b: 2 }
+>fn : () => {    a: 1;    b: 2;}
+>a : 1
+>b : 2
+
+let a: number;
+>a : number
+
+let b: number;
+>b : number
+
+({ a, b } = fn());
+>({ a, b } = fn()) : { a: 1; b: 2; }
+>{ a, b } = fn() : { a: 1; b: 2; }
+>{ a, b } : { a: number; b: number; }
+>a : number
+>b : number
+>fn() : { a: 1; b: 2; }
+>fn : () => { a: 1; b: 2; }
+
+{ a, b } = fn();
+>a, b : number
+>a : number
+>b : number
+>fn() : { a: 1; b: 2; }
+>fn : () => { a: 1; b: 2; }
+
+({ a, b } =
+>({ a, b } =fn()) : { a: 1; b: 2; }
+>{ a, b } =fn() : { a: 1; b: 2; }
+>{ a, b } : { a: number; b: number; }
+>a : number
+>b : number
+
+fn());
+>fn() : { a: 1; b: 2; }
+>fn : () => { a: 1; b: 2; }
+
+{ a, b }
+>a, b : number
+>a : number
+>b : number
+
+= fn();
+>fn() : { a: 1; b: 2; }
+>fn : () => { a: 1; b: 2; }
+

tests/cases/compiler/destructionAssignmentError.ts

@@ -0,0 +1,12 @@
+declare function fn(): { a: 1, b: 2 }
+let a: number;
+let b: number;
+
+({ a, b } = fn());
+{ a, b } = fn();
+
+({ a, b } =
+fn());
+
+{ a, b }
+= fn();