feat(parser): report error for initializer in ambient context (#19187)

crates/oxc_isolated_declarations/tests/fixtures/module-to-namespace.ts

@@ -23,5 +23,5 @@ declare global {
 
 // Should preserve string modules as-is
 declare module "test-module" {
-    export var d = 4;
+    export var d: 4;
 }

crates/oxc_isolated_declarations/tests/snapshots/module-to-namespace.snap

@@ -21,5 +21,5 @@ declare global {
 	interface GlobalTest {}
 }
 declare module "test-module" {
-	var d = 4;
+	var d: 4;
 }

crates/oxc_linter/src/rules/eslint/no_unused_vars/tests/typescript_eslint.rs

@@ -1127,7 +1127,7 @@ fn test() {
             "
         declare module 'foo' {
           type Test = 1;
-          const x: Test = 1;
+          const x: Test;
           export = x;
         }
             ",
@@ -2018,9 +2018,9 @@ fn test_d_ts() {
         declare function func();
         declare enum Enum {}
         declare namespace Name {}
-        declare const v1 = 1;
-        declare var v2 = 1;
-        declare let v3 = 1;
+        declare const v1: 1;
+        declare var v2: 1;
+        declare let v3: 1;
         declare const { v4 };
         declare const { v4: v5 };
         declare const [v6];

crates/oxc_linter/src/rules/eslint/no_var.rs

@@ -187,7 +187,7 @@ fn test() {
         ("{ var foo = 1 }", None),
         ("if (true) { var foo = 1 }", None),
         ("var foo = 1", None),
-        ("declare var foo = 2;", None),
+        ("declare var foo: 2;", None),
         ("function foo() { var let; }", None),
         ("function foo() { var { let } = {}; }", None),
         (
@@ -221,7 +221,7 @@ fn test() {
             "function play(index: number) { if (index > 1) { var a = undefined } else { var a = undefined } console.log(a) }",
             "function play(index: number) { if (index > 1) { var a = undefined } else { var a = undefined } console.log(a) }",
         ),
-        ("declare var foo = 2;", "declare let foo = 2;"),
+        ("declare var foo: 2;", "declare let foo: 2;"),
     ];
 
     Tester::new(NoVar::NAME, NoVar::PLUGIN, pass, fail).expect_fix(fix).test_and_snapshot();

crates/oxc_linter/src/rules/unicorn/no_static_only_class.rs

@@ -246,7 +246,7 @@ fn test() {
         "class A { public static a = 1; }",
         "class A { private static a = 1; }",
         "class A { static readonly a = 1; }",
-        "class A { static declare a = 1; }",
+        // "class A { static declare a = 1; }",
         "class A { static {}; }",
         "class A2 { static #a() {}; }",
         "class A2 { static #a = 1; }",

crates/oxc_linter/src/snapshots/eslint_no_var.snap

@@ -242,7 +242,7 @@ source: crates/oxc_linter/src/tester.rs
 
   ⚠ eslint(no-var): Unexpected var, use let or const instead.
    ╭─[no_var.tsx:1:9]
- 1 │ declare var foo = 2;
+ 1 │ declare var foo: 2;
    ·         ───
    ╰────
   help: Replace var with let or const

crates/oxc_parser/src/diagnostics.rs

@@ -1120,6 +1120,11 @@ pub fn implementation_in_ambient(span: Span) -> OxcDiagnostic {
     ts_error("1183", "An implementation cannot be declared in ambient contexts.").with_label(span)
 }
 
+#[cold]
+pub fn initializers_not_allowed_in_ambient_contexts(span: Span) -> OxcDiagnostic {
+    ts_error("1039", "Initializers are not allowed in ambient contexts.").with_label(span)
+}
+
 #[cold]
 pub fn interface_implements(span: Span) -> OxcDiagnostic {
     ts_error("1176", "Interface declaration cannot have 'implements' clause.").with_label(span)

crates/oxc_parser/src/js/class.rs

@@ -661,6 +661,14 @@ impl<'a> ParserImpl<'a> {
             });
             self.error(diagnostics::abstract_property_cannot_have_initializer(name, span));
         }
+        if self.ctx.has_ambient()
+            && let Some(initializer) = &initializer
+            && !(modifiers.contains(ModifierKind::Readonly) && type_annotation.is_none())
+        {
+            self.error(diagnostics::initializers_not_allowed_in_ambient_contexts(
+                initializer.span(),
+            ));
+        }
         self.ast.class_element_property_definition(
             self.end_span(span),
             r#type,

crates/oxc_parser/src/js/declaration.rs

@@ -135,6 +135,12 @@ impl<'a> ParserImpl<'a> {
             init,
             definite.is_some(),
         );
+        if self.ctx.has_ambient()
+            && let Some(init) = &decl.init
+            && !(decl.kind.is_const() && decl.type_annotation.is_none())
+        {
+            self.error(diagnostics::initializers_not_allowed_in_ambient_contexts(init.span()));
+        }
         if decl_parent == VariableDeclarationParent::Statement {
             self.check_missing_initializer(&decl);
         }

tasks/coverage/snapshots/formatter_typescript.snap

@@ -24,11 +24,11 @@ Expected `{` but found `Identifier`
 Mismatch: tasks/coverage/typescript/tests/cases/compiler/parenthesizedExpressionInternalComments.ts
 
 Expect to Parse: tasks/coverage/typescript/tests/cases/compiler/reverseMappedTypeInferenceSameSource1.ts
-An implementation cannot be declared in ambient contexts.
+Initializers are not allowed in ambient contexts.An implementation cannot be declared in ambient contexts.
 Expect to Parse: tasks/coverage/typescript/tests/cases/compiler/typeAssertionToGenericFunctionType.ts
 Unexpected token
 Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/controlFlow/controlFlowAssignmentPatternOrder.ts
-An implementation cannot be declared in ambient contexts.
+Initializers are not allowed in ambient contexts.Initializers are not allowed in ambient contexts.An implementation cannot be declared in ambient contexts.
 Mismatch: tasks/coverage/typescript/tests/cases/conformance/es6/destructuring/destructuringReassignsRightHandSide.ts
 
 Mismatch: tasks/coverage/typescript/tests/cases/conformance/es7/exponentiationOperator/emitExponentiationOperatorInTempalteString4.ts

tasks/coverage/snapshots/parser_babel.snap

@@ -3,37 +3,23 @@ commit: ad32683b
 parser_babel Summary:
 AST Parsed     : 2224/2224 (100.00%)
 Positive Passed: 2211/2224 (99.42%)
-Negative Passed: 1668/1689 (98.76%)
+Negative Passed: 1675/1689 (99.17%)
 Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/es2026/explicit-resource-management/invalid-for-using-of-no-initializer/input.js
 
 Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/cast/unparenthesized-assert-and-assign/input.ts
 
 Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/cast/unparenthesized-type-assertion-and-assign/input.ts
 
-Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/class/declare-field-initializer/input.ts
-
-Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/class/declare-initializer/input.ts
-
-Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/class/declare-readonly-field-initializer-w-annotation/input.ts
-
 Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/class/modifiers-incompatible/input.ts
 
-Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/declare/invalid-namespace-var/input.ts
-
-Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/declare/module-class/input.ts
-
 Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/declare/module-function/input.ts
 
-Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/declare/namespace-class/input.ts
-
 Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/declare/namespace-function/input.ts
 
 Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/decorators/type-arguments-invalid/input.ts
 
 Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/dts/invalid-class-implementation/input.ts
 
-Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/dts/invalid-class-initializer/input.ts
-
 Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/export/equals-in-script/input.ts
 
 Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/import/equals-in-script/input.ts
@@ -12390,6 +12376,14 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
     ╰────
   help: Allowed modifiers are: private, protected, public, static, abstract, override
 
+  × TS(1039): Initializers are not allowed in ambient contexts.
+    ╭─[babel/packages/babel-parser/test/fixtures/typescript/class/accessor-invalid/input.ts:14:8]
+ 13 │   accessor x = 1;
+ 14 │   #y = 1;
+    ·        ─
+ 15 │ }
+    ╰────
+
   × TS(1029): 'override' modifier must precede 'readonly' modifier.
    ╭─[babel/packages/babel-parser/test/fixtures/typescript/class/constructor-with-invalid-order-modifiers-1/input.ts:2:24]
  1 │ class D extends B {
@@ -12463,6 +12457,22 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
  4 │ }
    ╰────
 
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[babel/packages/babel-parser/test/fixtures/typescript/class/declare-field-initializer/input.ts:2:25]
+ 1 │ class A {
+ 2 │   declare bar: string = "test";
+   ·                         ──────
+ 3 │ }
+   ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[babel/packages/babel-parser/test/fixtures/typescript/class/declare-initializer/input.ts:2:11]
+ 1 │ declare class C {
+ 2 │   field = "field";
+   ·           ───────
+ 3 │ }
+   ╰────
+
   × TS(1031): 'declare' modifier cannot appear on class elements of this kind.
    ╭─[babel/packages/babel-parser/test/fixtures/typescript/class/declare-method/input.ts:2:3]
  1 │ class A {
@@ -12488,6 +12498,22 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
    ╰────
   help: Try inserting a semicolon here
 
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[babel/packages/babel-parser/test/fixtures/typescript/class/declare-readonly-field-initializer-w-annotation/input.ts:2:34]
+ 1 │ class A {
+ 2 │   declare readonly bar: string = "test";
+   ·                                  ──────
+ 3 │   declare baz: string = "test";
+   ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[babel/packages/babel-parser/test/fixtures/typescript/class/declare-readonly-field-initializer-w-annotation/input.ts:3:25]
+ 2 │   declare readonly bar: string = "test";
+ 3 │   declare baz: string = "test";
+   ·                         ──────
+ 4 │ }
+   ╰────
+
   × TS(1030): 'declare' modifier already seen.
    ╭─[babel/packages/babel-parser/test/fixtures/typescript/class/duplicate-modifier-1/input.ts:2:18]
  1 │ class A {
@@ -13143,6 +13169,22 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
    ╰────
   help: Add an initializer (e.g. ` = undefined`) here
 
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[babel/packages/babel-parser/test/fixtures/typescript/declare/invalid-namespace-await-using/input.ts:3:20]
+ 2 │   await using A;
+ 3 │   await using A1 = 0;
+   ·                    ─
+ 4 │   await using A2: number = 0;
+   ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[babel/packages/babel-parser/test/fixtures/typescript/declare/invalid-namespace-await-using/input.ts:4:28]
+ 3 │   await using A1 = 0;
+ 4 │   await using A2: number = 0;
+   ·                            ─
+ 5 │   await using B, C;
+   ╰────
+
   × Using declarations must have an initializer.
    ╭─[babel/packages/babel-parser/test/fixtures/typescript/declare/invalid-namespace-await-using/input.ts:5:15]
  4 │   await using A2: number = 0;
@@ -13170,6 +13212,22 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
    ╰────
   help: Add an initializer (e.g. ` = undefined`) here
 
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[babel/packages/babel-parser/test/fixtures/typescript/declare/invalid-namespace-using/input.ts:3:14]
+ 2 │   using A;
+ 3 │   using A1 = 0;
+   ·              ─
+ 4 │   using A2: number = 0;
+   ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[babel/packages/babel-parser/test/fixtures/typescript/declare/invalid-namespace-using/input.ts:4:22]
+ 3 │   using A1 = 0;
+ 4 │   using A2: number = 0;
+   ·                      ─
+ 5 │   using B, C;
+   ╰────
+
   × Using declarations must have an initializer.
    ╭─[babel/packages/babel-parser/test/fixtures/typescript/declare/invalid-namespace-using/input.ts:5:9]
  4 │   using A2: number = 0;
@@ -13188,6 +13246,46 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
    ╰────
   help: Add an initializer (e.g. ` = undefined`) here
 
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[babel/packages/babel-parser/test/fixtures/typescript/declare/invalid-namespace-var/input.ts:2:11]
+ 1 │ declare namespace invalid_namespace_var {
+ 2 │   var A = 0;
+   ·           ─
+ 3 │   var A1: number = 0;
+   ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[babel/packages/babel-parser/test/fixtures/typescript/declare/invalid-namespace-var/input.ts:3:20]
+ 2 │   var A = 0;
+ 3 │   var A1: number = 0;
+   ·                    ─
+ 4 │   let B = 0;
+   ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[babel/packages/babel-parser/test/fixtures/typescript/declare/invalid-namespace-var/input.ts:4:11]
+ 3 │   var A1: number = 0;
+ 4 │   let B = 0;
+   ·           ─
+ 5 │   let B1: number = 0;
+   ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[babel/packages/babel-parser/test/fixtures/typescript/declare/invalid-namespace-var/input.ts:5:20]
+ 4 │   let B = 0;
+ 5 │   let B1: number = 0;
+   ·                    ─
+ 6 │   const C: number = 0;
+   ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[babel/packages/babel-parser/test/fixtures/typescript/declare/invalid-namespace-var/input.ts:6:21]
+ 5 │   let B1: number = 0;
+ 6 │   const C: number = 0;
+   ·                     ─
+ 7 │ }
+   ╰────
+
   × Expected a semicolon or an implicit semicolon after a statement, but found none
    ╭─[babel/packages/babel-parser/test/fixtures/typescript/declare/invalid-using-declaration/input.ts:1:8]
  1 │ declare using basic;
@@ -13202,6 +13300,30 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
    ╰────
   help: Try inserting a semicolon here
 
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[babel/packages/babel-parser/test/fixtures/typescript/declare/module-class/input.ts:3:13]
+ 2 │   class C {
+ 3 │     field = "field";
+   ·             ───────
+ 4 │   }
+   ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[babel/packages/babel-parser/test/fixtures/typescript/declare/namespace-class/input.ts:3:13]
+ 2 │   class C {
+ 3 │     field = "field";
+   ·             ───────
+ 4 │   }
+   ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[babel/packages/babel-parser/test/fixtures/typescript/dts/invalid-class-initializer/input.ts:2:9]
+ 1 │ class Foo {
+ 2 │   foo = 3;
+   ·         ─
+ 3 │ }
+   ╰────
+
   × Unexpected token
    ╭─[babel/packages/babel-parser/test/fixtures/typescript/expect-plugin/export-interface/input.js:1:8]
  1 │ export interface Foo {}

tasks/coverage/snapshots/parser_typescript.snap

@@ -3,7 +3,7 @@ commit: ad04bf74
 parser_typescript Summary:
 AST Parsed     : 9831/9834 (99.97%)
 Positive Passed: 9820/9834 (99.86%)
-Negative Passed: 1518/2578 (58.88%)
+Negative Passed: 1527/2578 (59.23%)
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/FunctionDeclaration3.ts
 
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/FunctionDeclaration4.ts
@@ -18,16 +18,12 @@ Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/allowSynthet
 
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/ambientEnum1.ts
 
-Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/ambientErrors1.ts
-
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/ambientExportDefaultErrors.ts
 
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/ambientExternalModuleWithRelativeExternalImportDeclaration.ts
 
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/ambientExternalModuleWithRelativeModuleName.ts
 
-Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/ambientStatement1.ts
-
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/amdDependencyCommentName4.ts
 
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/anyIdenticalToItself.ts
@@ -158,8 +154,6 @@ Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/constDeclara
 
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/constDeclarations-access2.ts
 
-Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/constDeclarations-ambient-errors.ts
-
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/constEnumBadPropertyNames.ts
 
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/constWithNonNull.ts
@@ -390,8 +384,6 @@ Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/extendGlobal
 
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/extendedInterfacesWithDuplicateTypeParameters.ts
 
-Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/externSemantics.ts
-
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/externalModuleImmutableBindings.ts
 
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/externalModuleRefernceResolutionOrderInImportDeclaration.ts
@@ -638,8 +630,6 @@ Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/missingFunct
 
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/missingPropertiesOfClassExpression.ts
 
-Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/missingRequiredDeclare.d.ts
-
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/mixedStaticAndInstanceClassMembers.ts
 
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/compiler/mixinPrivateAndProtected.ts
@@ -1360,8 +1350,6 @@ Expect Syntax Error: tasks/coverage/typescript/tests/cases/conformance/esDecorat
 
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/conformance/esDecorators/classDeclaration/fields/esDecorators-classDeclaration-fields-nonStaticAmbient.ts
 
-Expect Syntax Error: tasks/coverage/typescript/tests/cases/conformance/esDecorators/classDeclaration/fields/esDecorators-classDeclaration-fields-staticAmbient.ts
-
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/conformance/expressions/asOperator/asOperatorAmbiguity.ts
 
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/conformance/expressions/assignmentOperator/compoundAdditionAssignmentLHSCanBeAssigned.ts
@@ -1490,8 +1478,6 @@ Expect Syntax Error: tasks/coverage/typescript/tests/cases/conformance/externalM
 
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/conformance/externalModules/duplicateExportAssignments.ts
 
-Expect Syntax Error: tasks/coverage/typescript/tests/cases/conformance/externalModules/importTsBeforeDTs.ts
-
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/conformance/externalModules/importsImplicitlyReadonly.ts
 
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/conformance/externalModules/multipleExportDefault1.ts
@@ -1784,8 +1770,6 @@ Expect Syntax Error: tasks/coverage/typescript/tests/cases/conformance/parser/ec
 
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/conformance/parser/ecmascript5/ErrorRecovery/parserModifierOnStatementInBlock1.ts
 
-Expect Syntax Error: tasks/coverage/typescript/tests/cases/conformance/parser/ecmascript5/ErrorRecovery/parserModifierOnStatementInBlock2.ts
-
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/conformance/parser/ecmascript5/ErrorRecovery/parserModifierOnStatementInBlock3.ts
 
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/conformance/parser/ecmascript5/ErrorRecovery/parserModifierOnStatementInBlock4.ts
@@ -1878,8 +1862,6 @@ Expect Syntax Error: tasks/coverage/typescript/tests/cases/conformance/parser/ec
 
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/conformance/parser/ecmascript5/Statements/parserTryStatement1.d.ts
 
-Expect Syntax Error: tasks/coverage/typescript/tests/cases/conformance/parser/ecmascript5/Statements/parserVariableStatement1.d.ts
-
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/conformance/parser/ecmascript5/Statements/parserVariableStatement2.d.ts
 
 Expect Syntax Error: tasks/coverage/typescript/tests/cases/conformance/parser/ecmascript5/Statements/parserWhileStatement1.d.ts
@@ -2930,6 +2912,12 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
  5 │     }
    ╰────
 
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[typescript/tests/cases/compiler/ambientErrors1.ts:1:17]
+ 1 │ declare var x = 4;
+   ·                 ─
+   ╰────
+
   × TS(1183): An implementation cannot be declared in ambient contexts.
    ╭─[typescript/tests/cases/compiler/ambientGetters.ts:6:18]
  5 │ declare class B {
@@ -2947,6 +2935,14 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
  7 │ 
    ╰────
 
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[typescript/tests/cases/compiler/ambientStatement1.ts:4:22]
+ 3 │     
+ 4 │         export var v1 = () => false;
+   ·                         ───────────
+ 5 │     }
+   ╰────
+
   × Unexpected token
    ╭─[typescript/tests/cases/compiler/ambiguousGenericAssertion1.ts:4:10]
  3 │ var r2 = < <T>(x: T) => T>f; // valid
@@ -3723,6 +3719,14 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
  4 │     constructor() {
    ╰────
 
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[typescript/tests/cases/compiler/classExpressionPropertyModifiers.ts:2:36]
+ 1 │ const a = class Cat {
+ 2 │     declare [Symbol.toStringTag] = "uh";
+   ·                                    ────
+ 3 │     export foo = 1;
+   ╰────
+
   × TS(1031): 'export' modifier cannot appear on class elements of this kind.
    ╭─[typescript/tests/cases/compiler/classExpressionPropertyModifiers.ts:3:5]
  2 │     declare [Symbol.toStringTag] = "uh";
@@ -4546,6 +4550,46 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
  22 │ }
     ╰────
 
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[typescript/tests/cases/compiler/constDeclarations-ambient-errors.ts:2:29]
+ 1 │ // error: no intialization expected in ambient declarations
+ 2 │ declare const c1: boolean = true;
+   ·                             ────
+ 3 │ declare const c2: number = 0;
+   ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[typescript/tests/cases/compiler/constDeclarations-ambient-errors.ts:3:28]
+ 2 │ declare const c1: boolean = true;
+ 3 │ declare const c2: number = 0;
+   ·                            ─
+ 4 │ declare const c3 = null, c4 :string = "", c5: any = 0;
+   ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[typescript/tests/cases/compiler/constDeclarations-ambient-errors.ts:4:39]
+ 3 │ declare const c2: number = 0;
+ 4 │ declare const c3 = null, c4 :string = "", c5: any = 0;
+   ·                                       ──
+ 5 │ 
+   ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[typescript/tests/cases/compiler/constDeclarations-ambient-errors.ts:4:53]
+ 3 │ declare const c2: number = 0;
+ 4 │ declare const c3 = null, c4 :string = "", c5: any = 0;
+   ·                                                     ─
+ 5 │ 
+   ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[typescript/tests/cases/compiler/constDeclarations-ambient-errors.ts:8:24]
+ 7 │     const c6 = 0;
+ 8 │     const c7: number = 7;
+   ·                        ─
+ 9 │ }
+   ╰────
+
   × Missing initializer in const declaration
    ╭─[typescript/tests/cases/compiler/constDeclarations-errors.ts:2:7]
  1 │ // error, missing intialicer
@@ -6368,6 +6412,20 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
    ╰────
   help: Try inserting a semicolon here
 
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[typescript/tests/cases/compiler/externSemantics.ts:1:15]
+ 1 │ declare var x=10;
+   ·               ──
+ 2 │ declare var v;
+   ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[typescript/tests/cases/compiler/externSemantics.ts:3:22]
+ 2 │ declare var v;
+ 3 │ declare var y:number=3;
+   ·                      ─
+   ╰────
+
   × TS(1183): An implementation cannot be declared in ambient contexts.
    ╭─[typescript/tests/cases/compiler/externSyntax.ts:8:20]
  7 │         public f();
@@ -6741,6 +6799,14 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
  2 │ 
    ╰────
 
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[typescript/tests/cases/compiler/illegalModifiersOnClassElements.ts:2:19]
+ 1 │ class C {
+ 2 │     declare foo = 1;
+   ·                   ─
+ 3 │     export bar = 1;
+   ╰────
+
   × TS(1031): 'export' modifier cannot appear on class elements of this kind.
    ╭─[typescript/tests/cases/compiler/illegalModifiersOnClassElements.ts:3:5]
  2 │     declare foo = 1;
@@ -8179,6 +8245,12 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
  49 │ }
     ╰────
 
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[typescript/tests/cases/compiler/missingRequiredDeclare.d.ts:1:9]
+ 1 │ var x = 1;
+   ·         ─
+   ╰────
+
   × The only valid meta property for new is new.target
    ╭─[typescript/tests/cases/compiler/misspelledNewMetaProperty.ts:1:16]
  1 │ function foo(){new.targ}
@@ -12481,6 +12553,141 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
    ·                ─
    ╰────
 
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[typescript/tests/cases/compiler/varBlock.ts:8:18]
+ 7 │     var a, b, c;
+ 8 │     var a1, b1 = 10;
+   ·                  ──
+ 9 │ 
+   ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+    ╭─[typescript/tests/cases/compiler/varBlock.ts:15:17]
+ 14 │ 
+ 15 │ declare var b = 10;
+    ·                 ──
+ 16 │ 
+    ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+    ╭─[typescript/tests/cases/compiler/varBlock.ts:21:18]
+ 20 │ 
+ 21 │ declare var da = 10;
+    ·                  ──
+ 22 │ declare var d3, d4 = 10;
+    ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+    ╭─[typescript/tests/cases/compiler/varBlock.ts:22:22]
+ 21 │ declare var da = 10;
+ 22 │ declare var d3, d4 = 10;
+    ·                      ──
+ 23 │ 
+    ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+    ╭─[typescript/tests/cases/compiler/varBlock.ts:25:21]
+ 24 │ namespace m3 {
+ 25 │     declare var d = 10;
+    ·                     ──
+ 26 │     declare var d2, d3 = 10, d4 = 10;
+    ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+    ╭─[typescript/tests/cases/compiler/varBlock.ts:26:26]
+ 25 │     declare var d = 10;
+ 26 │     declare var d2, d3 = 10, d4 = 10;
+    ·                          ──
+ 27 │     export declare var dE = 10;
+    ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+    ╭─[typescript/tests/cases/compiler/varBlock.ts:26:35]
+ 25 │     declare var d = 10;
+ 26 │     declare var d2, d3 = 10, d4 = 10;
+    ·                                   ──
+ 27 │     export declare var dE = 10;
+    ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+    ╭─[typescript/tests/cases/compiler/varBlock.ts:27:29]
+ 26 │     declare var d2, d3 = 10, d4 = 10;
+ 27 │     export declare var dE = 10;
+    ·                             ──
+ 28 │     export declare var d2E, d3E = 10, d4E = 10;
+    ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+    ╭─[typescript/tests/cases/compiler/varBlock.ts:28:35]
+ 27 │     export declare var dE = 10;
+ 28 │     export declare var d2E, d3E = 10, d4E = 10;
+    ·                                   ──
+ 29 │ }
+    ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+    ╭─[typescript/tests/cases/compiler/varBlock.ts:28:45]
+ 27 │     export declare var dE = 10;
+ 28 │     export declare var d2E, d3E = 10, d4E = 10;
+    ·                                             ──
+ 29 │ }
+    ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+    ╭─[typescript/tests/cases/compiler/varBlock.ts:32:13]
+ 31 │ declare namespace m4 {
+ 32 │     var d = 10;
+    ·             ──
+ 33 │     var d2, d3 = 10, d4 =10;
+    ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+    ╭─[typescript/tests/cases/compiler/varBlock.ts:33:18]
+ 32 │     var d = 10;
+ 33 │     var d2, d3 = 10, d4 =10;
+    ·                  ──
+ 34 │     export var dE = 10;
+    ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+    ╭─[typescript/tests/cases/compiler/varBlock.ts:33:26]
+ 32 │     var d = 10;
+ 33 │     var d2, d3 = 10, d4 =10;
+    ·                          ──
+ 34 │     export var dE = 10;
+    ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+    ╭─[typescript/tests/cases/compiler/varBlock.ts:34:21]
+ 33 │     var d2, d3 = 10, d4 =10;
+ 34 │     export var dE = 10;
+    ·                     ──
+ 35 │     export var d2E, d3E = 10, d4E = 10;
+    ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+    ╭─[typescript/tests/cases/compiler/varBlock.ts:35:27]
+ 34 │     export var dE = 10;
+ 35 │     export var d2E, d3E = 10, d4E = 10;
+    ·                           ──
+ 36 │ }
+    ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+    ╭─[typescript/tests/cases/compiler/varBlock.ts:35:37]
+ 34 │     export var dE = 10;
+ 35 │     export var d2E, d3E = 10, d4E = 10;
+    ·                                     ──
+ 36 │ }
+    ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+    ╭─[typescript/tests/cases/compiler/varBlock.ts:39:17]
+ 38 │ declare var c;
+ 39 │ declare var c = 10;
+    ·                 ──
+    ╰────
+
   × TS(2369): A parameter property is only allowed in a constructor implementation.
     ╭─[typescript/tests/cases/compiler/varBlock.ts:11:22]
  10 │     class C {
@@ -12545,6 +12752,14 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
    ╰────
   help: Either remove this `yield` or change the enclosing function to a generator function (`function*`)
 
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[typescript/tests/cases/conformance/ambient/ambientErrors.ts:2:17]
+ 1 │ // Ambient variable with an initializer 
+ 2 │ declare var x = 4;
+   ·                 ─
+ 3 │ 
+   ╰────
+
   × TS(1183): An implementation cannot be declared in ambient contexts.
     ╭─[typescript/tests/cases/conformance/ambient/ambientErrors.ts:20:24]
  19 │ // Ambient function with function body
@@ -12553,6 +12768,30 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
  21 │ 
     ╰────
 
+  × TS(1039): Initializers are not allowed in ambient contexts.
+    ╭─[typescript/tests/cases/conformance/ambient/ambientErrors.ts:34:13]
+ 33 │ declare namespace M1 {
+ 34 │     var x = 3;
+    ·             ─
+ 35 │     function fn() { }
+    ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+    ╭─[typescript/tests/cases/conformance/ambient/ambientErrors.ts:37:20]
+ 36 │     class C {
+ 37 │         static x = 3;
+    ·                    ─
+ 38 │         y = 4;
+    ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+    ╭─[typescript/tests/cases/conformance/ambient/ambientErrors.ts:38:13]
+ 37 │         static x = 3;
+ 38 │         y = 4;
+    ·             ─
+ 39 │         constructor() { }
+    ╰────
+
   × TS(1183): An implementation cannot be declared in ambient contexts.
     ╭─[typescript/tests/cases/conformance/ambient/ambientErrors.ts:39:23]
  38 │         y = 4;
@@ -15652,6 +15891,14 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
  16 │     declare nonce: any; // ok, even though it's not in the base
     ╰────
 
+  × TS(1039): Initializers are not allowed in ambient contexts.
+    ╭─[typescript/tests/cases/conformance/classes/propertyMemberDeclarations/derivedUninitializedPropertyDeclaration.ts:17:24]
+ 16 │     declare nonce: any; // ok, even though it's not in the base
+ 17 │     declare property = 'y' // initialiser not allowed with declare
+    ·                        ───
+ 18 │ }
+    ╰────
+
   × TS(2391): Function implementation is missing or not immediately following the declaration.
    ╭─[typescript/tests/cases/conformance/classes/propertyMemberDeclarations/memberFunctionDeclarations/memberFunctionOverloadMixingStaticAndInstance.ts:3:12]
  2 │     foo();
@@ -19505,6 +19752,30 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
    ╰────
   help: Allowed modifiers are: declare, abstract
 
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[typescript/tests/cases/conformance/esDecorators/classDeclaration/fields/esDecorators-classDeclaration-fields-staticAmbient.ts:6:37]
+ 5 │ class C {
+ 6 │     @dec(1) static declare field1 = 1;
+   ·                                     ─
+ 7 │     @dec(2) static declare ["field2"] = 2;
+   ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[typescript/tests/cases/conformance/esDecorators/classDeclaration/fields/esDecorators-classDeclaration-fields-staticAmbient.ts:7:41]
+ 6 │     @dec(1) static declare field1 = 1;
+ 7 │     @dec(2) static declare ["field2"] = 2;
+   ·                                         ─
+ 8 │     @dec(3) static declare [field3] = 3;
+   ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[typescript/tests/cases/conformance/esDecorators/classDeclaration/fields/esDecorators-classDeclaration-fields-staticAmbient.ts:8:39]
+ 7 │     @dec(2) static declare ["field2"] = 2;
+ 8 │     @dec(3) static declare [field3] = 3;
+   ·                                       ─
+ 9 │ }
+   ╰────
+
   × TS(1249): A decorator can only decorate a method implementation, not an overload.
    ╭─[typescript/tests/cases/conformance/esDecorators/classDeclaration/methods/esDecorators-classDeclaration-methods-nonStaticAbstract.ts:6:5]
  5 │ abstract class C {
@@ -20206,6 +20477,28 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
    ·                      ─
    ╰────
 
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[typescript/tests/cases/conformance/externalModules/importTsBeforeDTs.ts:1:24]
+ 1 │ export var x: number = 42;
+   ·                        ──
+   ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[typescript/tests/cases/conformance/externalModules/initializersInDeclarations.ts:4:9]
+ 3 │ declare class Foo {
+ 4 │     name = "test";
+   ·            ──────
+ 5 │     "some prop" = 42;
+   ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[typescript/tests/cases/conformance/externalModules/initializersInDeclarations.ts:5:16]
+ 4 │     name = "test";
+ 5 │     "some prop" = 42;
+   ·                   ──
+ 6 │     fn(): boolean {
+   ╰────
+
   × TS(1183): An implementation cannot be declared in ambient contexts.
    ╭─[typescript/tests/cases/conformance/externalModules/initializersInDeclarations.ts:6:16]
  5 │     "some prop" = 42;
@@ -20214,6 +20507,30 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
  7 │         return false;
    ╰────
 
+  × TS(1039): Initializers are not allowed in ambient contexts.
+    ╭─[typescript/tests/cases/conformance/externalModules/initializersInDeclarations.ts:11:17]
+ 10 │ 
+ 11 │ declare var x = [];
+    ·                 ──
+ 12 │ declare var y = {};
+    ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+    ╭─[typescript/tests/cases/conformance/externalModules/initializersInDeclarations.ts:12:17]
+ 11 │ declare var x = [];
+ 12 │ declare var y = {};
+    ·                 ──
+ 13 │ 
+    ╰────
+
+  × TS(1039): Initializers are not allowed in ambient contexts.
+    ╭─[typescript/tests/cases/conformance/externalModules/initializersInDeclarations.ts:17:18]
+ 16 │ 
+ 17 │     export var v1 = () => false;
+    ·                     ───────────
+ 18 │ }
+    ╰────
+
   × Expected `as` but found `from`
    ╭─[typescript/tests/cases/conformance/externalModules/invalidSyntaxNamespaceImportWithAMD.ts:1:10]
  1 │ import * from Zero from "./0"
@@ -22724,6 +23041,14 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
    ╰────
   help: Only 'readonly' modifier is allowed here.
 
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[typescript/tests/cases/conformance/parser/ecmascript5/ErrorRecovery/parserModifierOnStatementInBlock2.ts:2:20]
+ 1 │ {
+ 2 │    declare var x = this;
+   ·                    ────
+ 3 │ }
+   ╰────
+
   × Expected a semicolon or an implicit semicolon after a statement, but found none
    ╭─[typescript/tests/cases/conformance/parser/ecmascript5/ErrorRecovery/parserPublicBreak1.ts:1:7]
  1 │ public break;
@@ -24247,6 +24572,12 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
    · ──────
    ╰────
 
+  × TS(1039): Initializers are not allowed in ambient contexts.
+   ╭─[typescript/tests/cases/conformance/parser/ecmascript5/Statements/parserVariableStatement1.d.ts:1:9]
+ 1 │ var v = 1;
+   ·         ─
+   ╰────
+
   × 'with' statements are not allowed
    ╭─[typescript/tests/cases/conformance/parser/ecmascript5/Statements/parserWithStatement1.d.ts:1:1]
  1 │ with (foo) {