Restore #3529 (#3640)

Co-authored-by: Anders Hejlsberg <andersh@microsoft.com>
Co-authored-by: Gabriela Araujo Britto <gabrielaa@CPC-gabri-8SHBT.localdomain>

Author: 3 people

internal/checker/checker.go

@@ -1653,12 +1653,15 @@ func isES2015OrLaterConstructorName(s string) bool {
 }
 
 func (c *Checker) maybeMappedType(node *ast.Node, symbol *ast.Symbol) bool {
-	for ast.IsComputedPropertyName(node) || ast.IsPropertySignatureDeclaration(node) {
+	for {
 		node = node.Parent
+		if !(ast.IsComputedPropertyName(node) || ast.IsPropertySignatureDeclaration(node)) {
+			break
+		}
 	}
 	if ast.IsTypeLiteralNode(node) && len(node.Members()) == 1 {
 		t := c.getDeclaredTypeOfSymbol(symbol)
-		return t.flags&TypeFlagsUnion != 0 && c.allTypesAssignableToKind(t, TypeFlagsStringOrNumberLiteral)
+		return t.flags&TypeFlagsUnion != 0 && c.allTypesAssignableToKindEx(t, TypeFlagsStringOrNumberLiteral, true /*strict*/)
 	}
 	return false
 }

testdata/baselines/reference/submodule/compiler/typeUsedAsTypeLiteralIndex.errors.txt

@@ -1,6 +1,6 @@
-typeUsedAsTypeLiteralIndex.ts(3,6): error TS2693: 'K' only refers to a type, but is being used as a value here.
-typeUsedAsTypeLiteralIndex.ts(13,6): error TS2693: 'K2' only refers to a type, but is being used as a value here.
-typeUsedAsTypeLiteralIndex.ts(18,6): error TS2693: 'K3' only refers to a type, but is being used as a value here.
+typeUsedAsTypeLiteralIndex.ts(3,6): error TS2690: 'K' only refers to a type, but is being used as a value here. Did you mean to use 'P in K'?
+typeUsedAsTypeLiteralIndex.ts(13,6): error TS2690: 'K2' only refers to a type, but is being used as a value here. Did you mean to use 'K in K2'?
+typeUsedAsTypeLiteralIndex.ts(18,6): error TS2690: 'K3' only refers to a type, but is being used as a value here. Did you mean to use 'K in K3'?
 typeUsedAsTypeLiteralIndex.ts(23,6): error TS2693: 'K4' only refers to a type, but is being used as a value here.
 
 
@@ -9,7 +9,7 @@ typeUsedAsTypeLiteralIndex.ts(23,6): error TS2693: 'K4' only refers to a type, b
     type T = {
         [K]: number;  // Did you mean to use 'P in K'?
          ~
-!!! error TS2693: 'K' only refers to a type, but is being used as a value here.
+!!! error TS2690: 'K' only refers to a type, but is being used as a value here. Did you mean to use 'P in K'?
     }
 
     const K1 = Symbol();
@@ -21,14 +21,14 @@ typeUsedAsTypeLiteralIndex.ts(23,6): error TS2693: 'K4' only refers to a type, b
     type T2 = {
         [K2]: number;  // Did you mean to use 'K in K2'?
          ~~
-!!! error TS2693: 'K2' only refers to a type, but is being used as a value here.
+!!! error TS2690: 'K2' only refers to a type, but is being used as a value here. Did you mean to use 'K in K2'?
     }
 
     type K3 = number | string;
     type T3 = {
         [K3]: number; // Did you mean to use 'K in K3'?
          ~~
-!!! error TS2693: 'K3' only refers to a type, but is being used as a value here.
+!!! error TS2690: 'K3' only refers to a type, but is being used as a value here. Did you mean to use 'K in K3'?
     }
 
     type K4 = number | string;

testdata/baselines/reference/submoduleTriaged/compiler/typeUsedAsTypeLiteralIndex.errors.txt.diff

@@ -103,10 +103,6 @@ compiler/multiLinePropertyAccessAndArrowFunctionIndent1.errors.txt.diff
 compiler/parseErrorIncorrectReturnToken.errors.txt.diff
 conformance/parserStatementIsNotAMemberVariableDeclaration1(alwaysstrict=true).errors.txt.diff
 
-# TS2690 (with "Did you mean 'P in K'?" mapped type suggestion) changed to TS2693 (generic "refers to a type, but is being used as a value") — mapped type suggestion lost
-## https://github.com/microsoft/typescript-go/issues/3509
-compiler/typeUsedAsTypeLiteralIndex.errors.txt.diff
-
 # Unicode escapes in identifier names now displayed as literal characters
 ## https://github.com/microsoft/typescript-go/issues/3511
 conformance/parser.numericSeparators.decmialNegative.errors.txt.diff