Fix multiple issues related to extreme symbol merging (#2755)

ahejlsberg · web-flow · commit a5c64bdf11df · 2026-02-11T18:39:44.000Z
diff --git a/internal/checker/checker.go b/internal/checker/checker.go
@@ -21484,7 +21484,7 @@ func (c *Checker) fillMissingTypeArguments(typeArguments []*Type, typeParameters
 		return nil
 	}
 	numTypeArguments := len(typeArguments)
-	if isJavaScriptImplicitAny || (numTypeArguments >= minTypeArgumentCount && numTypeArguments < numTypeParameters) {
+	if isJavaScriptImplicitAny || numTypeArguments < numTypeParameters {
 		result := make([]*Type, numTypeParameters)
 		copy(result, typeArguments)
 		// Map invalid forward references in default types to the error type
@@ -22771,10 +22771,10 @@ func (c *Checker) createNormalizedTupleType(target *Type, elementTypes []*Type)
 	}
 	if d.combinedFlags&ElementFlagsVariadic != 0 {
 		for i, e := range elementTypes {
-			if d.elementInfos[i].flags&ElementFlagsVariadic != 0 && e.flags&(TypeFlagsNever|TypeFlagsUnion) != 0 {
+			if i < len(d.elementInfos) && d.elementInfos[i].flags&ElementFlagsVariadic != 0 && e.flags&(TypeFlagsNever|TypeFlagsUnion) != 0 {
 				// Transform [A, ...(X | Y | Z)] into [A, ...X] | [A, ...Y] | [A, ...Z]
 				checkTypes := core.MapIndex(elementTypes, func(t *Type, i int) *Type {
-					if d.elementInfos[i].flags&ElementFlagsVariadic != 0 {
+					if i < len(d.elementInfos) && d.elementInfos[i].flags&ElementFlagsVariadic != 0 {
 						return t
 					}
 					return c.unknownType
@@ -22787,15 +22787,20 @@ func (c *Checker) createNormalizedTupleType(target *Type, elementTypes []*Type)
 			}
 		}
 	}
-	// We have optional, rest, or variadic n that may need normalizing. Normalization ensures that all variadic
-	// n are generic and that the tuple type has one of the following layouts, disregarding variadic n:
-	// (1) Zero or more required n, followed by zero or more optional n, followed by zero or one rest element.
-	// (2) Zero or more required n, followed by a rest element, followed by zero or more required n.
-	// In either layout, zero or more generic variadic n may be present at any location.
+	// We have optional, rest, or variadic elements that may need normalizing. Normalization ensures that all variadic
+	// elements are generic and that the tuple type has one of the following layouts, disregarding variadic elements:
+	// (1) Zero or more required elements, followed by zero or more optional elements, followed by zero or one rest element.
+	// (2) Zero or more required elements, followed by a rest element, followed by zero or more required elements.
+	// In either layout, zero or more generic variadic elements may be present at any location.
+	// Note that the element types may contain an extra 'this' type argument that we want to ignore during normalization
+	// and then just append to the normalized element types.
 	n := &TupleNormalizer{}
-	if !n.normalize(c, elementTypes, d.elementInfos) {
+	if !n.normalize(c, elementTypes[:len(d.elementInfos)], d.elementInfos) {
 		return c.errorType
 	}
+	if len(elementTypes) > len(d.elementInfos) {
+		n.types = append(n.types, elementTypes[len(d.elementInfos)])
+	}
 	tupleTarget := c.getTupleTargetType(n.infos, d.readonly)
 	switch {
 	case tupleTarget == c.emptyGenericType:
@@ -23515,7 +23520,6 @@ func (c *Checker) evaluateEntity(expr *ast.Node, location *ast.Node) evaluator.R
 				name := expr.AsElementAccessExpression().ArgumentExpression.Text()
 				member := rootSymbol.Exports[name]
 				if member != nil {
-					debug.Assert(ast.GetSourceFileOfNode(member.ValueDeclaration) == ast.GetSourceFileOfNode(rootSymbol.ValueDeclaration))
 					if location != nil {
 						return c.evaluateEnumMember(expr, member, location)
 					}
diff --git a/internal/parser/parser.go b/internal/parser/parser.go
@@ -863,7 +863,7 @@ func (p *Parser) parseExpectedMatchingBrackets(openKind ast.Kind, closeKind ast.
 		return
 	}
 	if lastError != nil {
-		related := ast.NewDiagnostic(nil, core.NewTextRange(openPosition, openPosition+1), diagnostics.The_parser_expected_to_find_a_1_to_match_the_0_token_here, scanner.TokenToString(openKind), scanner.TokenToString(closeKind))
+		related := ast.NewDiagnostic(nil, core.NewTextRange(openPosition, openPosition), diagnostics.The_parser_expected_to_find_a_1_to_match_the_0_token_here, scanner.TokenToString(openKind), scanner.TokenToString(closeKind))
 		lastError.AddRelatedInfo(related)
 	}
 }
@@ -2925,7 +2925,7 @@ func (p *Parser) parseImportType() *ast.Node {
 			if len(p.diagnostics) != 0 {
 				lastDiagnostic := p.diagnostics[len(p.diagnostics)-1]
 				if lastDiagnostic.Code() == diagnostics.X_0_expected.Code() {
-					related := ast.NewDiagnostic(nil, core.NewTextRange(openBracePosition, openBracePosition+1), diagnostics.The_parser_expected_to_find_a_1_to_match_the_0_token_here, "{", "}")
+					related := ast.NewDiagnostic(nil, core.NewTextRange(openBracePosition, openBracePosition), diagnostics.The_parser_expected_to_find_a_1_to_match_the_0_token_here, "{", "}")
 					lastDiagnostic.AddRelatedInfo(related)
 				}
 			}
@@ -2972,7 +2972,7 @@ func (p *Parser) parseImportAttributes(token ast.Kind, skipKeyword bool) *ast.No
 			if len(p.diagnostics) != 0 {
 				lastDiagnostic := p.diagnostics[len(p.diagnostics)-1]
 				if lastDiagnostic.Code() == diagnostics.X_0_expected.Code() {
-					related := ast.NewDiagnostic(nil, core.NewTextRange(openBracePosition, openBracePosition+1), diagnostics.The_parser_expected_to_find_a_1_to_match_the_0_token_here, "{", "}")
+					related := ast.NewDiagnostic(nil, core.NewTextRange(openBracePosition, openBracePosition), diagnostics.The_parser_expected_to_find_a_1_to_match_the_0_token_here, "{", "}")
 					lastDiagnostic.AddRelatedInfo(related)
 				}
 			}
diff --git a/testdata/baselines/reference/submodule/conformance/instantiationExpressions.types b/testdata/baselines/reference/submodule/conformance/instantiationExpressions.types
@@ -18,8 +18,8 @@ function f1() {
 >f1 : () => void
 
     let f0 = fx<>;  // Error
->f0 : { <T>(x: T): T; <T>(x: T, n: number): T; <T, U>(t: [T, U]): [T, U]; }
->fx<> : { <T>(x: T): T; <T>(x: T, n: number): T; <T, U>(t: [T, U]): [T, U]; }
+>f0 : { (x: unknown): unknown; (x: unknown, n: number): unknown; (t: [unknown, unknown]): [unknown, unknown]; }
+>fx<> : { (x: unknown): unknown; (x: unknown, n: number): unknown; (t: [unknown, unknown]): [unknown, unknown]; }
 >fx : { <T>(x: T): T; <T>(x: T, n: number): T; <T, U>(t: [T, U]): [T, U]; }
 
     let f1 = fx<string>;  // { (x: string): string; (x: string, n: number): string; }
@@ -39,7 +39,7 @@ function f1() {
 }
 
 type T10 = typeof fx<>;  // Error
->T10 : { <T>(x: T): T; <T>(x: T, n: number): T; <T, U>(t: [T, U]): [T, U]; }
+>T10 : { (x: unknown): unknown; (x: unknown, n: number): unknown; (t: [unknown, unknown]): [unknown, unknown]; }
 >fx : { <T>(x: T): T; <T>(x: T, n: number): T; <T, U>(t: [T, U]): [T, U]; }
 
 type T11 = typeof fx<string>;  // { (x: string): string; (x: string, n: number): string; }
@@ -58,8 +58,8 @@ function f2() {
 >f2 : () => void
 
     const A0 = Array<>;  // Error
->A0 : { <T>(arrayLength: number): T[]; <T>(...items: T[]): T[]; new <T>(arrayLength: number): T[]; new <T>(...items: T[]): T[]; isArray(arg: any): arg is any[]; readonly prototype: any[]; from<T>(arrayLike: ArrayLike<T>): T[]; from<T, U>(arrayLike: ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; from<T>(iterable: ArrayLike<T> | Iterable<T>): T[]; from<T, U>(iterable: ArrayLike<T> | Iterable<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; of<T>(...items: T[]): T[]; readonly [Symbol.species]: ArrayConstructor; }
->Array<> : { <T>(arrayLength: number): T[]; <T>(...items: T[]): T[]; new <T>(arrayLength: number): T[]; new <T>(...items: T[]): T[]; isArray(arg: any): arg is any[]; readonly prototype: any[]; from<T>(arrayLike: ArrayLike<T>): T[]; from<T, U>(arrayLike: ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; from<T>(iterable: ArrayLike<T> | Iterable<T>): T[]; from<T, U>(iterable: ArrayLike<T> | Iterable<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; of<T>(...items: T[]): T[]; readonly [Symbol.species]: ArrayConstructor; }
+>A0 : { (arrayLength: number): unknown[]; (...items: unknown[]): unknown[]; new (arrayLength: number): unknown[]; new (...items: unknown[]): unknown[]; isArray(arg: any): arg is any[]; readonly prototype: any[]; from<T>(arrayLike: ArrayLike<T>): T[]; from<T, U>(arrayLike: ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; from<T>(iterable: ArrayLike<T> | Iterable<T>): T[]; from<T, U>(iterable: ArrayLike<T> | Iterable<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; of<T>(...items: T[]): T[]; readonly [Symbol.species]: ArrayConstructor; }
+>Array<> : { (arrayLength: number): unknown[]; (...items: unknown[]): unknown[]; new (arrayLength: number): unknown[]; new (...items: unknown[]): unknown[]; isArray(arg: any): arg is any[]; readonly prototype: any[]; from<T>(arrayLike: ArrayLike<T>): T[]; from<T, U>(arrayLike: ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; from<T>(iterable: ArrayLike<T> | Iterable<T>): T[]; from<T, U>(iterable: ArrayLike<T> | Iterable<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; of<T>(...items: T[]): T[]; readonly [Symbol.species]: ArrayConstructor; }
 >Array : ArrayConstructor
 
     const A1 = Array<string>;  // new (...) => string[]
@@ -74,7 +74,7 @@ function f2() {
 }
 
 type T20 = typeof Array<>;  // Error
->T20 : { <T>(arrayLength: number): T[]; <T>(...items: T[]): T[]; new <T>(arrayLength: number): T[]; new <T>(...items: T[]): T[]; isArray(arg: any): arg is any[]; readonly prototype: any[]; from<T>(arrayLike: ArrayLike<T>): T[]; from<T, U>(arrayLike: ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; from<T>(iterable: ArrayLike<T> | Iterable<T>): T[]; from<T, U>(iterable: ArrayLike<T> | Iterable<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; of<T>(...items: T[]): T[]; readonly [Symbol.species]: ArrayConstructor; }
+>T20 : { (arrayLength: number): unknown[]; (...items: unknown[]): unknown[]; new (arrayLength: number): unknown[]; new (...items: unknown[]): unknown[]; isArray(arg: any): arg is any[]; readonly prototype: any[]; from<T>(arrayLike: ArrayLike<T>): T[]; from<T, U>(arrayLike: ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; from<T>(iterable: ArrayLike<T> | Iterable<T>): T[]; from<T, U>(iterable: ArrayLike<T> | Iterable<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; of<T>(...items: T[]): T[]; readonly [Symbol.species]: ArrayConstructor; }
 >Array : ArrayConstructor
 
 type T21 = typeof Array<string>;  // new (...) => string[]
diff --git a/testdata/baselines/reference/submodule/conformance/instantiationExpressions.types.diff b/testdata/baselines/reference/submodule/conformance/instantiationExpressions.types.diff
@@ -20,7 +20,22 @@
  >t : [T, U]
 
  function f1() {
-@@= skipped -41, +41 lines =@@
+ >f1 : () => void
+
+     let f0 = fx<>;  // Error
+->f0 : { <T>(x: T): T; <T>(x: T, n: number): T; <T, U>(t: [T, U]): [T, U]; }
+->fx<> : { <T>(x: T): T; <T>(x: T, n: number): T; <T, U>(t: [T, U]): [T, U]; }
++>f0 : { (x: unknown): unknown; (x: unknown, n: number): unknown; (t: [unknown, unknown]): [unknown, unknown]; }
++>fx<> : { (x: unknown): unknown; (x: unknown, n: number): unknown; (t: [unknown, unknown]): [unknown, unknown]; }
+ >fx : { <T>(x: T): T; <T>(x: T, n: number): T; <T, U>(t: [T, U]): [T, U]; }
+
+     let f1 = fx<string>;  // { (x: string): string; (x: string, n: number): string; }
+@@= skipped -37, +37 lines =@@
+ }
+
+ type T10 = typeof fx<>;  // Error
+->T10 : { <T>(x: T): T; <T>(x: T, n: number): T; <T, U>(t: [T, U]): [T, U]; }
++>T10 : { (x: unknown): unknown; (x: unknown, n: number): unknown; (t: [unknown, unknown]): [unknown, unknown]; }
  >fx : { <T>(x: T): T; <T>(x: T, n: number): T; <T, U>(t: [T, U]): [T, U]; }
 
  type T11 = typeof fx<string>;  // { (x: string): string; (x: string, n: number): string; }
@@ -44,8 +59,8 @@
      const A0 = Array<>;  // Error
 ->A0 : ArrayConstructor
 ->Array<> : ArrayConstructor
-+>A0 : { <T>(arrayLength: number): T[]; <T>(...items: T[]): T[]; new <T>(arrayLength: number): T[]; new <T>(...items: T[]): T[]; isArray(arg: any): arg is any[]; readonly prototype: any[]; from<T>(arrayLike: ArrayLike<T>): T[]; from<T, U>(arrayLike: ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; from<T>(iterable: ArrayLike<T> | Iterable<T>): T[]; from<T, U>(iterable: ArrayLike<T> | Iterable<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; of<T>(...items: T[]): T[]; readonly [Symbol.species]: ArrayConstructor; }
-+>Array<> : { <T>(arrayLength: number): T[]; <T>(...items: T[]): T[]; new <T>(arrayLength: number): T[]; new <T>(...items: T[]): T[]; isArray(arg: any): arg is any[]; readonly prototype: any[]; from<T>(arrayLike: ArrayLike<T>): T[]; from<T, U>(arrayLike: ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; from<T>(iterable: ArrayLike<T> | Iterable<T>): T[]; from<T, U>(iterable: ArrayLike<T> | Iterable<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; of<T>(...items: T[]): T[]; readonly [Symbol.species]: ArrayConstructor; }
++>A0 : { (arrayLength: number): unknown[]; (...items: unknown[]): unknown[]; new (arrayLength: number): unknown[]; new (...items: unknown[]): unknown[]; isArray(arg: any): arg is any[]; readonly prototype: any[]; from<T>(arrayLike: ArrayLike<T>): T[]; from<T, U>(arrayLike: ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; from<T>(iterable: ArrayLike<T> | Iterable<T>): T[]; from<T, U>(iterable: ArrayLike<T> | Iterable<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; of<T>(...items: T[]): T[]; readonly [Symbol.species]: ArrayConstructor; }
++>Array<> : { (arrayLength: number): unknown[]; (...items: unknown[]): unknown[]; new (arrayLength: number): unknown[]; new (...items: unknown[]): unknown[]; isArray(arg: any): arg is any[]; readonly prototype: any[]; from<T>(arrayLike: ArrayLike<T>): T[]; from<T, U>(arrayLike: ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; from<T>(iterable: ArrayLike<T> | Iterable<T>): T[]; from<T, U>(iterable: ArrayLike<T> | Iterable<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; of<T>(...items: T[]): T[]; readonly [Symbol.species]: ArrayConstructor; }
  >Array : ArrayConstructor
 
      const A1 = Array<string>;  // new (...) => string[]
@@ -65,7 +80,7 @@
 
  type T20 = typeof Array<>;  // Error
 ->T20 : ArrayConstructor
-+>T20 : { <T>(arrayLength: number): T[]; <T>(...items: T[]): T[]; new <T>(arrayLength: number): T[]; new <T>(...items: T[]): T[]; isArray(arg: any): arg is any[]; readonly prototype: any[]; from<T>(arrayLike: ArrayLike<T>): T[]; from<T, U>(arrayLike: ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; from<T>(iterable: ArrayLike<T> | Iterable<T>): T[]; from<T, U>(iterable: ArrayLike<T> | Iterable<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; of<T>(...items: T[]): T[]; readonly [Symbol.species]: ArrayConstructor; }
++>T20 : { (arrayLength: number): unknown[]; (...items: unknown[]): unknown[]; new (arrayLength: number): unknown[]; new (...items: unknown[]): unknown[]; isArray(arg: any): arg is any[]; readonly prototype: any[]; from<T>(arrayLike: ArrayLike<T>): T[]; from<T, U>(arrayLike: ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; from<T>(iterable: ArrayLike<T> | Iterable<T>): T[]; from<T, U>(iterable: ArrayLike<T> | Iterable<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; of<T>(...items: T[]): T[]; readonly [Symbol.species]: ArrayConstructor; }
  >Array : ArrayConstructor
 
  type T21 = typeof Array<string>;  // new (...) => string[]
@@ -79,7 +94,7 @@
  >Array : ArrayConstructor
 
  declare class C<T> {
-@@= skipped -133, +133 lines =@@
+@@= skipped -137, +137 lines =@@
  }
 
  function f15(f: { new <T>(a: T): T, <U>(a: U, b: number): U[] }) {

Original file line number	Diff line number	Diff line change
`@@ -863,7 +863,7 @@ func (p *Parser) parseExpectedMatchingBrackets(openKind ast.Kind, closeKind ast.`
`863`	`863`	`return`
`864`	`864`	`}`
`865`	`865`	`if lastError != nil {`
`866`		`- related := ast.NewDiagnostic(nil, core.NewTextRange(openPosition, openPosition+1), diagnostics.The_parser_expected_to_find_a_1_to_match_the_0_token_here, scanner.TokenToString(openKind), scanner.TokenToString(closeKind))`
	`866`	`+ related := ast.NewDiagnostic(nil, core.NewTextRange(openPosition, openPosition), diagnostics.The_parser_expected_to_find_a_1_to_match_the_0_token_here, scanner.TokenToString(openKind), scanner.TokenToString(closeKind))`
`867`	`867`	`lastError.AddRelatedInfo(related)`
`868`	`868`	`}`
`869`	`869`	`}`
`@@ -2925,7 +2925,7 @@ func (p Parser) parseImportType() ast.Node {`
`2925`	`2925`	`if len(p.diagnostics) != 0 {`
`2926`	`2926`	`lastDiagnostic := p.diagnostics[len(p.diagnostics)-1]`
`2927`	`2927`	`if lastDiagnostic.Code() == diagnostics.X_0_expected.Code() {`
`2928`		`- related := ast.NewDiagnostic(nil, core.NewTextRange(openBracePosition, openBracePosition+1), diagnostics.The_parser_expected_to_find_a_1_to_match_the_0_token_here, "{", "}")`
	`2928`	`+ related := ast.NewDiagnostic(nil, core.NewTextRange(openBracePosition, openBracePosition), diagnostics.The_parser_expected_to_find_a_1_to_match_the_0_token_here, "{", "}")`
`2929`	`2929`	`lastDiagnostic.AddRelatedInfo(related)`
`2930`	`2930`	`}`
`2931`	`2931`	`}`
`@@ -2972,7 +2972,7 @@ func (p Parser) parseImportAttributes(token ast.Kind, skipKeyword bool) ast.No`
`2972`	`2972`	`if len(p.diagnostics) != 0 {`
`2973`	`2973`	`lastDiagnostic := p.diagnostics[len(p.diagnostics)-1]`
`2974`	`2974`	`if lastDiagnostic.Code() == diagnostics.X_0_expected.Code() {`
`2975`		`- related := ast.NewDiagnostic(nil, core.NewTextRange(openBracePosition, openBracePosition+1), diagnostics.The_parser_expected_to_find_a_1_to_match_the_0_token_here, "{", "}")`
	`2975`	`+ related := ast.NewDiagnostic(nil, core.NewTextRange(openBracePosition, openBracePosition), diagnostics.The_parser_expected_to_find_a_1_to_match_the_0_token_here, "{", "}")`
`2976`	`2976`	`lastDiagnostic.AddRelatedInfo(related)`
`2977`	`2977`	`}`
`2978`	`2978`	`}`