Get [type] parameter types from @type tag (microsoft#26694)

sandersn · web-flow · commit a2e4a282e799 · 2018-08-27T16:52:35.000-07:00
* Get [type] parameter types from @type tag Previously only the return type was used in cases like this: ```js /** @type {<T>(param?: T) => T | undefined} */ function g(param) { return param; } ``` Now the type parameters from the type tag are used, and the compiler gets the type of the parameter by using the position in the signature of the type tag. Fixes microsoft#25618 * Fix split ifs according to PR comments
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -4699,6 +4699,12 @@ namespace ts {
                         return getReturnTypeOfSignature(getterSignature);
                     }
                 }
+                if (isInJavaScriptFile(declaration)) {
+                    const typeTag = getJSDocType(func);
+                    if (typeTag && isFunctionTypeNode(typeTag)) {
+                        return getTypeAtPosition(getSignatureFromDeclaration(typeTag), func.parameters.indexOf(declaration));
+                    }
+                }
                 // Use contextual parameter type if one is available
                 const type = declaration.symbol.escapedName === InternalSymbolName.This ? getContextualThisParameterType(func) : getContextuallyTypedParameterType(declaration);
                 if (type) {
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
@@ -5116,7 +5116,20 @@ namespace ts {
             Debug.assert(node.parent.kind === SyntaxKind.JSDocComment);
             return flatMap(node.parent.tags, tag => isJSDocTemplateTag(tag) ? tag.typeParameters : undefined) as ReadonlyArray<TypeParameterDeclaration>;
         }
-        return node.typeParameters || (isInJavaScriptFile(node) ? getJSDocTypeParameterDeclarations(node) : emptyArray);
+        if (node.typeParameters) {
+            return node.typeParameters;
+        }
+        if (isInJavaScriptFile(node)) {
+            const decls = getJSDocTypeParameterDeclarations(node);
+            if (decls.length) {
+                return decls;
+            }
+            const typeTag = getJSDocType(node);
+            if (typeTag && isFunctionTypeNode(typeTag) && typeTag.typeParameters) {
+                return typeTag.typeParameters;
+            }
+        }
+        return emptyArray;
     }
 
     export function getEffectiveConstraintOfTypeParameter(node: TypeParameterDeclaration): TypeNode | undefined {
diff --git a/tests/baselines/reference/typeTagWithGenericSignature.symbols b/tests/baselines/reference/typeTagWithGenericSignature.symbols
@@ -0,0 +1,15 @@
+=== tests/cases/conformance/jsdoc/bug25618.js ===
+/** @type {<T>(param?: T) => T | undefined} */
+function typed(param) {
+>typed : Symbol(typed, Decl(bug25618.js, 0, 0))
+>param : Symbol(param, Decl(bug25618.js, 1, 15))
+
+    return param;
+>param : Symbol(param, Decl(bug25618.js, 1, 15))
+}
+
+var n = typed(1);
+>n : Symbol(n, Decl(bug25618.js, 5, 3))
+>typed : Symbol(typed, Decl(bug25618.js, 0, 0))
+
+
diff --git a/tests/baselines/reference/typeTagWithGenericSignature.types b/tests/baselines/reference/typeTagWithGenericSignature.types
@@ -0,0 +1,17 @@
+=== tests/cases/conformance/jsdoc/bug25618.js ===
+/** @type {<T>(param?: T) => T | undefined} */
+function typed(param) {
+>typed : <T>(param: T | undefined) => T | undefined
+>param : T | undefined
+
+    return param;
+>param : T | undefined
+}
+
+var n = typed(1);
+>n : number | undefined
+>typed(1) : 1 | undefined
+>typed : <T>(param: T | undefined) => T | undefined
+>1 : 1
+
+
diff --git a/tests/cases/conformance/jsdoc/typeTagWithGenericSignature.ts b/tests/cases/conformance/jsdoc/typeTagWithGenericSignature.ts
@@ -0,0 +1,13 @@
+// @checkJs: true
+// @allowJs: true
+// @noEmit: true
+// @strict: true
+// @Filename: bug25618.js
+
+/** @type {<T>(param?: T) => T | undefined} */
+function typed(param) {
+    return param;
+}
+
+var n = typed(1);
+

Original file line number	Diff line number	Diff line change
`@@ -4699,6 +4699,12 @@ namespace ts {`
`4699`	`4699`	`return getReturnTypeOfSignature(getterSignature);`
`4700`	`4700`	`}`
`4701`	`4701`	`}`
	`4702`	`+ if (isInJavaScriptFile(declaration)) {`
	`4703`	`+ const typeTag = getJSDocType(func);`
	`4704`	`+ if (typeTag && isFunctionTypeNode(typeTag)) {`
	`4705`	`+ return getTypeAtPosition(getSignatureFromDeclaration(typeTag), func.parameters.indexOf(declaration));`
	`4706`	`+ }`
	`4707`	`+ }`
`4702`	`4708`	`// Use contextual parameter type if one is available`
`4703`	`4709`	`const type = declaration.symbol.escapedName === InternalSymbolName.This ? getContextualThisParameterType(func) : getContextuallyTypedParameterType(declaration);`
`4704`	`4710`	`if (type) {`