Infer from parameters annotated using JSDoc (microsoft#55400)

Author: Andarist

src/compiler/checker.ts

@@ -35600,13 +35600,11 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         const len = signature.parameters.length - (signatureHasRestParameter(signature) ? 1 : 0);
         for (let i = 0; i < len; i++) {
             const declaration = signature.parameters[i].valueDeclaration as ParameterDeclaration;
-            if (declaration.type) {
-                const typeNode = getEffectiveTypeAnnotationNode(declaration);
-                if (typeNode) {
-                    const source = addOptionality(getTypeFromTypeNode(typeNode), /*isProperty*/ false, isOptionalDeclaration(declaration));
-                    const target = getTypeAtPosition(context, i);
-                    inferTypes(inferenceContext.inferences, source, target);
-                }
+            const typeNode = getEffectiveTypeAnnotationNode(declaration);
+            if (typeNode) {
+                const source = addOptionality(getTypeFromTypeNode(typeNode), /*isProperty*/ false, isOptionalDeclaration(declaration));
+                const target = getTypeAtPosition(context, i);
+                inferTypes(inferenceContext.inferences, source, target);
             }
         }
     }

tests/baselines/reference/contravariantOnlyInferenceFromAnnotatedFunctionJs.symbols

@@ -0,0 +1,41 @@
+//// [tests/cases/compiler/contravariantOnlyInferenceFromAnnotatedFunctionJs.ts] ////
+
+=== index.js ===
+/**
+ * @typedef {{ [K in keyof B]: { fn: (a: A, b: B) => void; thing: B[K]; } }} Funcs
+ * @template A
+ * @template {Record<string, unknown>} B
+ */
+
+/**
+ * @template A
+ * @template {Record<string, unknown>} B
+ * @param {Funcs<A, B>} fns
+ * @returns {[A, B]}
+ */
+function foo(fns) {
+>foo : Symbol(foo, Decl(index.js, 0, 0))
+>fns : Symbol(fns, Decl(index.js, 12, 13))
+
+  return /** @type {any} */ (null);
+}
+
+const result = foo({
+>result : Symbol(result, Decl(index.js, 16, 5))
+>foo : Symbol(foo, Decl(index.js, 0, 0))
+
+  bar: {
+>bar : Symbol(bar, Decl(index.js, 16, 20))
+
+    fn:
+>fn : Symbol(fn, Decl(index.js, 17, 8))
+
+      /** @param {string} a */
+      (a) => {},
+>a : Symbol(a, Decl(index.js, 20, 7))
+
+    thing: "asd",
+>thing : Symbol(thing, Decl(index.js, 20, 16))
+
+  },
+});

tests/baselines/reference/contravariantOnlyInferenceFromAnnotatedFunctionJs.types

@@ -0,0 +1,47 @@
+//// [tests/cases/compiler/contravariantOnlyInferenceFromAnnotatedFunctionJs.ts] ////
+
+=== index.js ===
+/**
+ * @typedef {{ [K in keyof B]: { fn: (a: A, b: B) => void; thing: B[K]; } }} Funcs
+ * @template A
+ * @template {Record<string, unknown>} B
+ */
+
+/**
+ * @template A
+ * @template {Record<string, unknown>} B
+ * @param {Funcs<A, B>} fns
+ * @returns {[A, B]}
+ */
+function foo(fns) {
+>foo : <A, B extends Record<string, unknown>>(fns: Funcs<A, B>) => [A, B]
+>fns : Funcs<A, B>
+
+  return /** @type {any} */ (null);
+>(null) : any
+}
+
+const result = foo({
+>result : [string, { bar: string; }]
+>foo({  bar: {    fn:      /** @param {string} a */      (a) => {},    thing: "asd",  },}) : [string, { bar: string; }]
+>foo : <A, B extends Record<string, unknown>>(fns: Funcs<A, B>) => [A, B]
+>{  bar: {    fn:      /** @param {string} a */      (a) => {},    thing: "asd",  },} : { bar: { fn: (a: string) => void; thing: string; }; }
+
+  bar: {
+>bar : { fn: (a: string) => void; thing: string; }
+>{    fn:      /** @param {string} a */      (a) => {},    thing: "asd",  } : { fn: (a: string) => void; thing: string; }
+
+    fn:
+>fn : (a: string) => void
+
+      /** @param {string} a */
+      (a) => {},
+>(a) => {} : (a: string) => void
+>a : string
+
+    thing: "asd",
+>thing : string
+>"asd" : "asd"
+
+  },
+});

tests/cases/compiler/contravariantOnlyInferenceFromAnnotatedFunctionJs.ts

@@ -0,0 +1,30 @@
+// @strict: true
+// @checkJs: true
+// @noEmit: true
+
+// @filename: index.js
+
+/**
+ * @typedef {{ [K in keyof B]: { fn: (a: A, b: B) => void; thing: B[K]; } }} Funcs
+ * @template A
+ * @template {Record<string, unknown>} B
+ */
+
+/**
+ * @template A
+ * @template {Record<string, unknown>} B
+ * @param {Funcs<A, B>} fns
+ * @returns {[A, B]}
+ */
+function foo(fns) {
+  return /** @type {any} */ (null);
+}
+
+const result = foo({
+  bar: {
+    fn:
+      /** @param {string} a */
+      (a) => {},
+    thing: "asd",
+  },
+});