Revert "Merge pull request microsoft#32071 from andrewbranch/bug/31070"

This reverts commit 327bc3c, reversing
changes made to c91e147.

Author: andrewbranch

src/compiler/checker.ts

@@ -13443,14 +13443,14 @@ namespace ts {
                         if (!isGenericMappedType(source)) {
                             const targetConstraint = getConstraintTypeFromMappedType(target);
                             const sourceKeys = getIndexType(source, /*stringsOnly*/ undefined, /*noIndexSignatures*/ true);
-                            const includeOptional = modifiers & MappedTypeModifiers.IncludeOptional;
-                            const filteredByApplicability = includeOptional ? intersectTypes(targetConstraint, sourceKeys) : undefined;
+                            const hasOptionalUnionKeys = modifiers & MappedTypeModifiers.IncludeOptional && targetConstraint.flags & TypeFlags.Union;
+                            const filteredByApplicability = hasOptionalUnionKeys ? filterType(targetConstraint, t => !!isRelatedTo(t, sourceKeys)) : undefined;
                             // A source type T is related to a target type { [P in Q]: X } if Q is related to keyof T and T[Q] is related to X.
                             // A source type T is related to a target type { [P in Q]?: X } if some constituent Q' of Q is related to keyof T and T[Q'] is related to X.
-                            if (includeOptional
+                            if (hasOptionalUnionKeys
                                     ? !(filteredByApplicability!.flags & TypeFlags.Never)
                                     : isRelatedTo(targetConstraint, sourceKeys)) {
-                                const indexingType = filteredByApplicability || getTypeParameterFromMappedType(target);
+                                const indexingType = hasOptionalUnionKeys ? filteredByApplicability! : getTypeParameterFromMappedType(target);
                                 const indexedAccessType = getIndexedAccessType(source, indexingType);
                                 const templateType = getTemplateTypeFromMappedType(target);
                                 if (result = isRelatedTo(indexedAccessType, templateType, reportErrors)) {

tests/baselines/reference/circularlyConstrainedMappedTypeContainingConditionalNoInfiniteInstantiationDepth.errors.txt

@@ -386,10 +386,4 @@ tests/cases/conformance/types/mapped/mappedTypeRelationships.ts(168,5): error TS
     function f82<T, K1 extends keyof T, K2 extends keyof T[K1]>(t: T, k1: K1, k2: K2): Partial<T[K1][K2]> {
         return t[k1][k2];
     }
-    
-    // #31070
-    type Numeric<T> = { [K in keyof T]?: number };
-    function f90<T extends { x: number }>() {
-        const n: Numeric<T> = { x: 1 };
-    }
 

tests/baselines/reference/mappedTypeRelationships.errors.txt

@@ -180,12 +180,6 @@ function f81<T, K extends keyof T>(t: T, k: K): Partial<T[K]> {
 function f82<T, K1 extends keyof T, K2 extends keyof T[K1]>(t: T, k1: K1, k2: K2): Partial<T[K1][K2]> {
     return t[k1][k2];
 }
-
-// #31070
-type Numeric<T> = { [K in keyof T]?: number };
-function f90<T extends { x: number }>() {
-    const n: Numeric<T> = { x: 1 };
-}
 
 
 //// [mappedTypeRelationships.js]
@@ -316,9 +310,6 @@ function f81(t, k) {
 function f82(t, k1, k2) {
     return t[k1][k2];
 }
-function f90() {
-    var n = { x: 1 };
-}
 
 
 //// [mappedTypeRelationships.d.ts]
@@ -402,9 +393,3 @@ declare function f76<T, U extends T, K extends keyof T>(x: {
 declare function f80<T>(t: T): Partial<T>;
 declare function f81<T, K extends keyof T>(t: T, k: K): Partial<T[K]>;
 declare function f82<T, K1 extends keyof T, K2 extends keyof T[K1]>(t: T, k1: K1, k2: K2): Partial<T[K1][K2]>;
-declare type Numeric<T> = {
-    [K in keyof T]?: number;
-};
-declare function f90<T extends {
-    x: number;
-}>(): void;

tests/baselines/reference/mappedTypeRelationships.js

@@ -805,22 +805,3 @@ function f82<T, K1 extends keyof T, K2 extends keyof T[K1]>(t: T, k1: K1, k2: K2
 >k2 : Symbol(k2, Decl(mappedTypeRelationships.ts, 178, 73))
 }
 
-// #31070
-type Numeric<T> = { [K in keyof T]?: number };
->Numeric : Symbol(Numeric, Decl(mappedTypeRelationships.ts, 180, 1))
->T : Symbol(T, Decl(mappedTypeRelationships.ts, 183, 13))
->K : Symbol(K, Decl(mappedTypeRelationships.ts, 183, 21))
->T : Symbol(T, Decl(mappedTypeRelationships.ts, 183, 13))
-
-function f90<T extends { x: number }>() {
->f90 : Symbol(f90, Decl(mappedTypeRelationships.ts, 183, 46))
->T : Symbol(T, Decl(mappedTypeRelationships.ts, 184, 13))
->x : Symbol(x, Decl(mappedTypeRelationships.ts, 184, 24))
-
-    const n: Numeric<T> = { x: 1 };
->n : Symbol(n, Decl(mappedTypeRelationships.ts, 185, 9))
->Numeric : Symbol(Numeric, Decl(mappedTypeRelationships.ts, 180, 1))
->T : Symbol(T, Decl(mappedTypeRelationships.ts, 184, 13))
->x : Symbol(x, Decl(mappedTypeRelationships.ts, 185, 27))
-}
-

tests/baselines/reference/mappedTypeRelationships.symbols

@@ -653,18 +653,3 @@ function f82<T, K1 extends keyof T, K2 extends keyof T[K1]>(t: T, k1: K1, k2: K2
 >k2 : K2
 }
 
-// #31070
-type Numeric<T> = { [K in keyof T]?: number };
->Numeric : Numeric<T>
-
-function f90<T extends { x: number }>() {
->f90 : <T extends { x: number; }>() => void
->x : number
-
-    const n: Numeric<T> = { x: 1 };
->n : Numeric<T>
->{ x: 1 } : { x: number; }
->x : number
->1 : 1
-}
-