Infer from constraints of type parameters in generic signatures

microsoft · Jan 8, 2025 · 80f7af3 · 80f7af3
1 parent c0b3ff2
commit 80f7af3
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Showing 4 changed files with 83 additions and 2 deletions.
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -26842,8 +26842,18 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 const targetSignatures = getSignaturesOfType(target, kind);
                 const targetLen = targetSignatures.length;
                 for (let i = 0; i < targetLen; i++) {
-                    const sourceIndex = Math.max(sourceLen - targetLen + i, 0);
-                    inferFromSignature(getBaseSignature(sourceSignatures[sourceIndex]), getErasedSignature(targetSignatures[i]));
+                    const sourceSignature = sourceSignatures[Math.max(sourceLen - targetLen + i, 0)];
+                    const targetSignature = targetSignatures[i];
+                    if (targetSignature.typeParameters && targetSignature.typeParameters.length === sourceSignature.typeParameters?.length) {
+                        for (let j = 0; j < targetSignature.typeParameters.length; j++) {
+                            const sourceTypeParameter = sourceSignature.typeParameters[j];
+                            const targetTypeParameter = targetSignature.typeParameters[j];
+                            if (sourceTypeParameter.constraint && targetTypeParameter.constraint) {
+                                inferFromTypes(sourceTypeParameter.constraint, targetTypeParameter.constraint);
+                            }
+                        }
+                    }
+                    inferFromSignature(getBaseSignature(sourceSignature), getErasedSignature(targetSignature));
                 }
             }
         }

diff --git a/tests/baselines/reference/inferenceFromGenericSignatureTypeParamConstraints1.symbols b/tests/baselines/reference/inferenceFromGenericSignatureTypeParamConstraints1.symbols
@@ -0,0 +1,32 @@
+//// [tests/cases/compiler/inferenceFromGenericSignatureTypeParamConstraints1.ts] ////
+
+=== inferenceFromGenericSignatureTypeParamConstraints1.ts ===
+// https://github.com/microsoft/TypeScript/issues/41040
+
+type InferGenericConstraint<Fn> = 
+>InferGenericConstraint : Symbol(InferGenericConstraint, Decl(inferenceFromGenericSignatureTypeParamConstraints1.ts, 0, 0))
+>Fn : Symbol(Fn, Decl(inferenceFromGenericSignatureTypeParamConstraints1.ts, 2, 28))
+
+    Fn extends <T extends infer Constraint>(arg: T) => any
+>Fn : Symbol(Fn, Decl(inferenceFromGenericSignatureTypeParamConstraints1.ts, 2, 28))
+>T : Symbol(T, Decl(inferenceFromGenericSignatureTypeParamConstraints1.ts, 3, 16))
+>Constraint : Symbol(Constraint, Decl(inferenceFromGenericSignatureTypeParamConstraints1.ts, 3, 31))
+>arg : Symbol(arg, Decl(inferenceFromGenericSignatureTypeParamConstraints1.ts, 3, 44))
+>T : Symbol(T, Decl(inferenceFromGenericSignatureTypeParamConstraints1.ts, 3, 16))
+
+        ? Constraint
+>Constraint : Symbol(Constraint, Decl(inferenceFromGenericSignatureTypeParamConstraints1.ts, 3, 31))
+
+        : never;
+
+type GenericFunctionExample = <T extends number>(arg: T) => void;
+>GenericFunctionExample : Symbol(GenericFunctionExample, Decl(inferenceFromGenericSignatureTypeParamConstraints1.ts, 5, 16))
+>T : Symbol(T, Decl(inferenceFromGenericSignatureTypeParamConstraints1.ts, 7, 31))
+>arg : Symbol(arg, Decl(inferenceFromGenericSignatureTypeParamConstraints1.ts, 7, 49))
+>T : Symbol(T, Decl(inferenceFromGenericSignatureTypeParamConstraints1.ts, 7, 31))
+
+type InferredConstraint = InferGenericConstraint<GenericFunctionExample>;
+>InferredConstraint : Symbol(InferredConstraint, Decl(inferenceFromGenericSignatureTypeParamConstraints1.ts, 7, 65))
+>InferGenericConstraint : Symbol(InferGenericConstraint, Decl(inferenceFromGenericSignatureTypeParamConstraints1.ts, 0, 0))
+>GenericFunctionExample : Symbol(GenericFunctionExample, Decl(inferenceFromGenericSignatureTypeParamConstraints1.ts, 5, 16))
+
diff --git a/tests/baselines/reference/inferenceFromGenericSignatureTypeParamConstraints1.types b/tests/baselines/reference/inferenceFromGenericSignatureTypeParamConstraints1.types
@@ -0,0 +1,26 @@
+//// [tests/cases/compiler/inferenceFromGenericSignatureTypeParamConstraints1.ts] ////
+
+=== inferenceFromGenericSignatureTypeParamConstraints1.ts ===
+// https://github.com/microsoft/TypeScript/issues/41040
+
+type InferGenericConstraint<Fn> = 
+>InferGenericConstraint : InferGenericConstraint<Fn>
+>                       : ^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+    Fn extends <T extends infer Constraint>(arg: T) => any
+>arg : T
+>    : ^
+
+        ? Constraint
+        : never;
+
+type GenericFunctionExample = <T extends number>(arg: T) => void;
+>GenericFunctionExample : GenericFunctionExample
+>                       : ^^^^^^^^^^^^^^^^^^^^^^
+>arg : T
+>    : ^
+
+type InferredConstraint = InferGenericConstraint<GenericFunctionExample>;
+>InferredConstraint : number
+>                   : ^^^^^^
+
diff --git a/tests/cases/compiler/inferenceFromGenericSignatureTypeParamConstraints1.ts b/tests/cases/compiler/inferenceFromGenericSignatureTypeParamConstraints1.ts
@@ -0,0 +1,13 @@
+// @noEmit: true
+// @strict: true
+
+// https://github.com/microsoft/TypeScript/issues/41040
+
+type InferGenericConstraint<Fn> = 
+    Fn extends <T extends infer Constraint>(arg: T) => any
+        ? Constraint
+        : never;
+
+type GenericFunctionExample = <T extends number>(arg: T) => void;
+
+type InferredConstraint = InferGenericConstraint<GenericFunctionExample>;