Normalize target type after null-stripping unions in relationship checks

src/compiler/checker.ts

@@ -17373,9 +17373,9 @@ namespace ts {
                     (target as UnionType).types.length <= 3 && maybeTypeOfKind(target, TypeFlags.Nullable)) {
                     const nullStrippedTarget = extractTypesOfKind(target, ~TypeFlags.Nullable);
                     if (!(nullStrippedTarget.flags & (TypeFlags.Union | TypeFlags.Never))) {
-                        if (source === nullStrippedTarget) return Ternary.True;
-                        target = nullStrippedTarget;
+                        target = getNormalizedType(nullStrippedTarget, /*writing*/ true);
                     }
+                    if (source === nullStrippedTarget) return Ternary.True;
                 }
 
                 if (relation === comparableRelation && !(target.flags & TypeFlags.Never) && isSimpleTypeRelatedTo(target, source, relation) ||

tests/baselines/reference/indexedAccessNormalization.js

@@ -0,0 +1,35 @@
+//// [indexedAccessNormalization.ts]
+// Repro from from #43152
+
+type MyMap<M extends object> = {
+    [K in keyof M]: {
+        x: number
+    }
+}
+
+declare function g<T>(value?: T): void;
+
+function f1<M extends object>(mymap: MyMap<M>, k: keyof M) {
+    const elemofM = mymap[k];
+    g(elemofM);
+}
+
+function f2<M extends object>(mymap: MyMap<M>, k: keyof M, z: { x: number }) {
+    const q1: MyMap<M>[keyof M] = z;
+    const q2: MyMap<M>[keyof M] | undefined = z;
+    const q3: MyMap<M>[keyof M] | string = z;
+}
+
+
+//// [indexedAccessNormalization.js]
+"use strict";
+// Repro from from #43152
+function f1(mymap, k) {
+    var elemofM = mymap[k];
+    g(elemofM);
+}
+function f2(mymap, k, z) {
+    var q1 = z;
+    var q2 = z;
+    var q3 = z;
+}

tests/baselines/reference/indexedAccessNormalization.symbols

@@ -0,0 +1,74 @@
+=== tests/cases/compiler/indexedAccessNormalization.ts ===
+// Repro from from #43152
+
+type MyMap<M extends object> = {
+>MyMap : Symbol(MyMap, Decl(indexedAccessNormalization.ts, 0, 0))
+>M : Symbol(M, Decl(indexedAccessNormalization.ts, 2, 11))
+
+    [K in keyof M]: {
+>K : Symbol(K, Decl(indexedAccessNormalization.ts, 3, 5))
+>M : Symbol(M, Decl(indexedAccessNormalization.ts, 2, 11))
+
+        x: number
+>x : Symbol(x, Decl(indexedAccessNormalization.ts, 3, 21))
+    }
+}
+
+declare function g<T>(value?: T): void;
+>g : Symbol(g, Decl(indexedAccessNormalization.ts, 6, 1))
+>T : Symbol(T, Decl(indexedAccessNormalization.ts, 8, 19))
+>value : Symbol(value, Decl(indexedAccessNormalization.ts, 8, 22))
+>T : Symbol(T, Decl(indexedAccessNormalization.ts, 8, 19))
+
+function f1<M extends object>(mymap: MyMap<M>, k: keyof M) {
+>f1 : Symbol(f1, Decl(indexedAccessNormalization.ts, 8, 39))
+>M : Symbol(M, Decl(indexedAccessNormalization.ts, 10, 12))
+>mymap : Symbol(mymap, Decl(indexedAccessNormalization.ts, 10, 30))
+>MyMap : Symbol(MyMap, Decl(indexedAccessNormalization.ts, 0, 0))
+>M : Symbol(M, Decl(indexedAccessNormalization.ts, 10, 12))
+>k : Symbol(k, Decl(indexedAccessNormalization.ts, 10, 46))
+>M : Symbol(M, Decl(indexedAccessNormalization.ts, 10, 12))
+
+    const elemofM = mymap[k];
+>elemofM : Symbol(elemofM, Decl(indexedAccessNormalization.ts, 11, 9))
+>mymap : Symbol(mymap, Decl(indexedAccessNormalization.ts, 10, 30))
+>k : Symbol(k, Decl(indexedAccessNormalization.ts, 10, 46))
+
+    g(elemofM);
+>g : Symbol(g, Decl(indexedAccessNormalization.ts, 6, 1))
+>elemofM : Symbol(elemofM, Decl(indexedAccessNormalization.ts, 11, 9))
+}
+
+function f2<M extends object>(mymap: MyMap<M>, k: keyof M, z: { x: number }) {
+>f2 : Symbol(f2, Decl(indexedAccessNormalization.ts, 13, 1))
+>M : Symbol(M, Decl(indexedAccessNormalization.ts, 15, 12))
+>mymap : Symbol(mymap, Decl(indexedAccessNormalization.ts, 15, 30))
+>MyMap : Symbol(MyMap, Decl(indexedAccessNormalization.ts, 0, 0))
+>M : Symbol(M, Decl(indexedAccessNormalization.ts, 15, 12))
+>k : Symbol(k, Decl(indexedAccessNormalization.ts, 15, 46))
+>M : Symbol(M, Decl(indexedAccessNormalization.ts, 15, 12))
+>z : Symbol(z, Decl(indexedAccessNormalization.ts, 15, 58))
+>x : Symbol(x, Decl(indexedAccessNormalization.ts, 15, 63))
+
+    const q1: MyMap<M>[keyof M] = z;
+>q1 : Symbol(q1, Decl(indexedAccessNormalization.ts, 16, 9))
+>MyMap : Symbol(MyMap, Decl(indexedAccessNormalization.ts, 0, 0))
+>M : Symbol(M, Decl(indexedAccessNormalization.ts, 15, 12))
+>M : Symbol(M, Decl(indexedAccessNormalization.ts, 15, 12))
+>z : Symbol(z, Decl(indexedAccessNormalization.ts, 15, 58))
+
+    const q2: MyMap<M>[keyof M] | undefined = z;
+>q2 : Symbol(q2, Decl(indexedAccessNormalization.ts, 17, 9))
+>MyMap : Symbol(MyMap, Decl(indexedAccessNormalization.ts, 0, 0))
+>M : Symbol(M, Decl(indexedAccessNormalization.ts, 15, 12))
+>M : Symbol(M, Decl(indexedAccessNormalization.ts, 15, 12))
+>z : Symbol(z, Decl(indexedAccessNormalization.ts, 15, 58))
+
+    const q3: MyMap<M>[keyof M] | string = z;
+>q3 : Symbol(q3, Decl(indexedAccessNormalization.ts, 18, 9))
+>MyMap : Symbol(MyMap, Decl(indexedAccessNormalization.ts, 0, 0))
+>M : Symbol(M, Decl(indexedAccessNormalization.ts, 15, 12))
+>M : Symbol(M, Decl(indexedAccessNormalization.ts, 15, 12))
+>z : Symbol(z, Decl(indexedAccessNormalization.ts, 15, 58))
+}
+

tests/baselines/reference/indexedAccessNormalization.types

@@ -0,0 +1,53 @@
+=== tests/cases/compiler/indexedAccessNormalization.ts ===
+// Repro from from #43152
+
+type MyMap<M extends object> = {
+>MyMap : MyMap<M>
+
+    [K in keyof M]: {
+        x: number
+>x : number
+    }
+}
+
+declare function g<T>(value?: T): void;
+>g : <T>(value?: T | undefined) => void
+>value : T | undefined
+
+function f1<M extends object>(mymap: MyMap<M>, k: keyof M) {
+>f1 : <M extends object>(mymap: MyMap<M>, k: keyof M) => void
+>mymap : MyMap<M>
+>k : keyof M
+
+    const elemofM = mymap[k];
+>elemofM : MyMap<M>[keyof M]
+>mymap[k] : MyMap<M>[keyof M]
+>mymap : MyMap<M>
+>k : keyof M
+
+    g(elemofM);
+>g(elemofM) : void
+>g : <T>(value?: T | undefined) => void
+>elemofM : MyMap<M>[keyof M]
+}
+
+function f2<M extends object>(mymap: MyMap<M>, k: keyof M, z: { x: number }) {
+>f2 : <M extends object>(mymap: MyMap<M>, k: keyof M, z: {    x: number;}) => void
+>mymap : MyMap<M>
+>k : keyof M
+>z : { x: number; }
+>x : number
+
+    const q1: MyMap<M>[keyof M] = z;
+>q1 : MyMap<M>[keyof M]
+>z : { x: number; }
+
+    const q2: MyMap<M>[keyof M] | undefined = z;
+>q2 : MyMap<M>[keyof M] | undefined
+>z : { x: number; }
+
+    const q3: MyMap<M>[keyof M] | string = z;
+>q3 : string | MyMap<M>[keyof M]
+>z : { x: number; }
+}
+

tests/cases/compiler/indexedAccessNormalization.ts

@@ -0,0 +1,22 @@
+// @strict: true
+
+// Repro from from #43152
+
+type MyMap<M extends object> = {
+    [K in keyof M]: {
+        x: number
+    }
+}
+
+declare function g<T>(value?: T): void;
+
+function f1<M extends object>(mymap: MyMap<M>, k: keyof M) {
+    const elemofM = mymap[k];
+    g(elemofM);
+}
+
+function f2<M extends object>(mymap: MyMap<M>, k: keyof M, z: { x: number }) {
+    const q1: MyMap<M>[keyof M] = z;
+    const q2: MyMap<M>[keyof M] | undefined = z;
+    const q3: MyMap<M>[keyof M] | string = z;
+}