Exclude the domain root from contextual typing literals except for type variables

Author: weswigham

src/compiler/checker.ts

@@ -18908,13 +18908,20 @@ namespace ts {
                 }
                 if (contextualType.flags & TypeFlags.TypeVariable) {
                     const constraint = getBaseConstraintOfType(contextualType) || emptyObjectType;
-                    return isLiteralOfContextualType(candidateLiteral, constraint);
+                    // A constraint of a literal domain causes the inference of literal types, ie `T extends string` contextually typing a `"foo"` causes `"foo"` to be the type
+                    return !!((constraint.flags & TypeFlags.String && maybeTypeOfKind(candidateLiteral, TypeFlags.StringLike)) ||
+                        (constraint.flags & TypeFlags.Number && maybeTypeOfKind(candidateLiteral, TypeFlags.NumberLike)) ||
+                        (constraint.flags & TypeFlags.Boolean && maybeTypeOfKind(candidateLiteral, TypeFlags.BooleanLike)) ||
+                        (constraint.flags & TypeFlags.ESSymbol && maybeTypeOfKind(candidateLiteral, TypeFlags.ESSymbolLike)) ||
+                        isLiteralOfContextualType(candidateLiteral, constraint)
+                    );
                 }
                 // No need to `maybeTypeOfKind` on the contextual type, as it can't be a union, _however_, `candidateLiteral` might still be one!
-                return !!((contextualType.flags & TypeFlags.StringLike && maybeTypeOfKind(candidateLiteral, TypeFlags.StringLike)) ||
-                    (contextualType.flags & TypeFlags.NumberLike && maybeTypeOfKind(candidateLiteral, TypeFlags.NumberLike)) ||
-                    (contextualType.flags & TypeFlags.BooleanLike && maybeTypeOfKind(candidateLiteral, TypeFlags.BooleanLike)) ||
-                    (contextualType.flags & TypeFlags.ESSymbolLike && maybeTypeOfKind(candidateLiteral, TypeFlags.ESSymbolLike))
+                // Please note: Only another literal in the same domain _and not the domain itself_ causes a literal type to be produced
+                return !!((contextualType.flags & TypeFlags.StringLike && !(contextualType.flags & TypeFlags.String) && maybeTypeOfKind(candidateLiteral, TypeFlags.StringLike)) ||
+                    (contextualType.flags & TypeFlags.NumberLike && !(contextualType.flags & TypeFlags.Number) && maybeTypeOfKind(candidateLiteral, TypeFlags.NumberLike)) ||
+                    (contextualType.flags & TypeFlags.BooleanLike && !(contextualType.flags & TypeFlags.Boolean) && maybeTypeOfKind(candidateLiteral, TypeFlags.BooleanLike)) ||
+                    (contextualType.flags & TypeFlags.ESSymbolLike && !(contextualType.flags & TypeFlags.ESSymbol) && maybeTypeOfKind(candidateLiteral, TypeFlags.ESSymbolLike))
                 );
             }
             return false;

tests/baselines/reference/ClassAndModuleThatMergeWithStaticFunctionAndExportedFunctionThatShareAName.types

@@ -9,7 +9,7 @@ class Point {
     static Origin(): Point { return { x: 0, y: 0 }; } // unexpected error here bug 840246
 >Origin : () => Point
 >Point : Point
->{ x: 0, y: 0 } : { x: 0; y: 0; }
+>{ x: 0, y: 0 } : { x: number; y: number; }
 >x : number
 >0 : 0
 >y : number
@@ -38,7 +38,7 @@ module A {
         static Origin(): Point { return { x: 0, y: 0 }; } // unexpected error here bug 840246
 >Origin : () => Point
 >Point : Point
->{ x: 0, y: 0 } : { x: 0; y: 0; }
+>{ x: 0, y: 0 } : { x: number; y: number; }
 >x : number
 >0 : 0
 >y : number

tests/baselines/reference/ClassAndModuleThatMergeWithStaticFunctionAndNonExportedFunctionThatShareAName.types

@@ -9,7 +9,7 @@ class Point {
     static Origin(): Point { return { x: 0, y: 0 }; }
 >Origin : () => Point
 >Point : Point
->{ x: 0, y: 0 } : { x: 0; y: 0; }
+>{ x: 0, y: 0 } : { x: number; y: number; }
 >x : number
 >0 : 0
 >y : number
@@ -38,7 +38,7 @@ module A {
         static Origin(): Point { return { x: 0, y: 0 }; }
 >Origin : () => Point
 >Point : Point
->{ x: 0, y: 0 } : { x: 0; y: 0; }
+>{ x: 0, y: 0 } : { x: number; y: number; }
 >x : number
 >0 : 0
 >y : number

tests/baselines/reference/ClassAndModuleThatMergeWithStaticVariableAndExportedVarThatShareAName.types

@@ -9,7 +9,7 @@ class Point {
     static Origin: Point = { x: 0, y: 0 };
 >Origin : Point
 >Point : Point
->{ x: 0, y: 0 } : { x: 0; y: 0; }
+>{ x: 0, y: 0 } : { x: number; y: number; }
 >x : number
 >0 : 0
 >y : number
@@ -38,7 +38,7 @@ module A {
         static Origin: Point = { x: 0, y: 0 };
 >Origin : Point
 >Point : Point
->{ x: 0, y: 0 } : { x: 0; y: 0; }
+>{ x: 0, y: 0 } : { x: number; y: number; }
 >x : number
 >0 : 0
 >y : number

tests/baselines/reference/ClassAndModuleThatMergeWithStaticVariableAndNonExportedVarThatShareAName.types

@@ -9,7 +9,7 @@ class Point {
     static Origin: Point = { x: 0, y: 0 };
 >Origin : Point
 >Point : Point
->{ x: 0, y: 0 } : { x: 0; y: 0; }
+>{ x: 0, y: 0 } : { x: number; y: number; }
 >x : number
 >0 : 0
 >y : number
@@ -38,7 +38,7 @@ module A {
         static Origin: Point = { x: 0, y: 0 };
 >Origin : Point
 >Point : Point
->{ x: 0, y: 0 } : { x: 0; y: 0; }
+>{ x: 0, y: 0 } : { x: number; y: number; }
 >x : number
 >0 : 0
 >y : number

tests/baselines/reference/ES5For-of30.types

@@ -5,7 +5,7 @@ var a: string, b: number;
 
 var tuple: [number, string] = [2, "3"];
 >tuple : [number, string]
->[2, "3"] : [2, "3"]
+>[2, "3"] : [number, string]
 >2 : 2
 >"3" : "3"
 

tests/baselines/reference/ES5For-ofTypeCheck3.types

@@ -1,7 +1,7 @@
 === tests/cases/conformance/statements/for-ofStatements/ES5For-ofTypeCheck3.ts ===
 var tuple: [string, number] = ["", 0];
 >tuple : [string, number]
->["", 0] : ["", 0]
+>["", 0] : [string, number]
 >"" : ""
 >0 : 0
 

tests/baselines/reference/ES5for-of32.types

@@ -20,9 +20,9 @@ for (let num of array) {
 >0 : 0
 
         array = [4,5,6]
->array = [4,5,6] : (4 | 5 | 6)[]
+>array = [4,5,6] : number[]
 >array : number[]
->[4,5,6] : (4 | 5 | 6)[]
+>[4,5,6] : number[]
 >4 : 4
 >5 : 5
 >6 : 6

tests/baselines/reference/ExportClassWithAccessibleTypesInTypeParameterConstraintsClassHeritageListMemberTypeAnnotations.types

@@ -15,7 +15,7 @@ module A {
     export var Origin: Point = { x: 0, y: 0 };
 >Origin : Point
 >Point : Point
->{ x: 0, y: 0 } : { x: 0; y: 0; }
+>{ x: 0, y: 0 } : { x: number; y: number; }
 >x : number
 >0 : 0
 >y : number
@@ -32,7 +32,7 @@ module A {
     export var Origin3d: Point3d = { x: 0, y: 0, z: 0 };
 >Origin3d : Point3d
 >Point3d : Point3d
->{ x: 0, y: 0, z: 0 } : { x: 0; y: 0; z: 0; }
+>{ x: 0, y: 0, z: 0 } : { x: number; y: number; z: number; }
 >x : number
 >0 : 0
 >y : number

tests/baselines/reference/ExportClassWithInaccessibleTypeInTypeParameterConstraint.types

@@ -15,7 +15,7 @@ module A {
     export var Origin: Point = { x: 0, y: 0 };
 >Origin : Point
 >Point : Point
->{ x: 0, y: 0 } : { x: 0; y: 0; }
+>{ x: 0, y: 0 } : { x: number; y: number; }
 >x : number
 >0 : 0
 >y : number
@@ -32,7 +32,7 @@ module A {
     export var Origin3d: Point3d = { x: 0, y: 0, z: 0 };
 >Origin3d : Point3d
 >Point3d : Point3d
->{ x: 0, y: 0, z: 0 } : { x: 0; y: 0; z: 0; }
+>{ x: 0, y: 0, z: 0 } : { x: number; y: number; z: number; }
 >x : number
 >0 : 0
 >y : number