Prefer non-partial signature match in non-generic case

src/compiler/checker.ts

@@ -13242,9 +13242,12 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         }
         let result: Signature[] | undefined;
         for (let i = 0; i < signatureLists.length; i++) {
-            // Allow matching non-generic signatures to have excess parameters and different return types.
+            // Allow matching non-generic signatures to have excess parameters (as a fallback if exact parameter match is not found) and different return types.
             // Prefer matching this types if possible.
-            const match = i === listIndex ? signature : findMatchingSignature(signatureLists[i], signature, /*partialMatch*/ true, /*ignoreThisTypes*/ false, /*ignoreReturnTypes*/ true);
+            const match = i === listIndex
+                ? signature
+                : findMatchingSignature(signatureLists[i], signature, /*partialMatch*/ false, /*ignoreThisTypes*/ false, /*ignoreReturnTypes*/ true)
+                    || findMatchingSignature(signatureLists[i], signature, /*partialMatch*/ true, /*ignoreThisTypes*/ false, /*ignoreReturnTypes*/ true);
             if (!match) {
                 return undefined;
             }

tests/baselines/reference/unionTypeCallSignatures6.errors.txt

@@ -6,12 +6,7 @@ unionTypeCallSignatures6.ts(38,4): error TS2349: This expression is not callable
 unionTypeCallSignatures6.ts(39,1): error TS2684: The 'this' context of type 'A & C & { f0: F0 | F3; f1: F1 | F3; f2: F1 | F4; f3: F3 | F4; f4: F3 | F5; }' is not assignable to method's 'this' of type 'B'.
   Property 'b' is missing in type 'A & C & { f0: F0 | F3; f1: F1 | F3; f2: F1 | F4; f3: F3 | F4; f4: F3 | F5; }' but required in type 'B'.
 unionTypeCallSignatures6.ts(48,1): error TS2684: The 'this' context of type 'void' is not assignable to method's 'this' of type 'A & B'.
-unionTypeCallSignatures6.ts(55,1): error TS2769: No overload matches this call.
-  Overload 1 of 2, '(this: A & B & C): void', gave the following error.
-    The 'this' context of type 'void' is not assignable to method's 'this' of type 'A & B & C'.
-      Type 'void' is not assignable to type 'A'.
-  Overload 2 of 2, '(this: A & B): void', gave the following error.
-    The 'this' context of type 'void' is not assignable to method's 'this' of type 'A & B'.
+unionTypeCallSignatures6.ts(55,1): error TS2684: The 'this' context of type 'void' is not assignable to method's 'this' of type 'A & B'.
 
 
 ==== unionTypeCallSignatures6.ts (6 errors) ====
@@ -85,10 +80,5 @@ unionTypeCallSignatures6.ts(55,1): error TS2769: No overload matches this call.
     declare var f4: F6 | F7;
     f4(); // error
     ~~~~
-!!! error TS2769: No overload matches this call.
-!!! error TS2769:   Overload 1 of 2, '(this: A & B & C): void', gave the following error.
-!!! error TS2769:     The 'this' context of type 'void' is not assignable to method's 'this' of type 'A & B & C'.
-!!! error TS2769:       Type 'void' is not assignable to type 'A'.
-!!! error TS2769:   Overload 2 of 2, '(this: A & B): void', gave the following error.
-!!! error TS2769:     The 'this' context of type 'void' is not assignable to method's 'this' of type 'A & B'.
+!!! error TS2684: The 'this' context of type 'void' is not assignable to method's 'this' of type 'A & B'.
 

tests/baselines/reference/unionTypeCallSignatures7.symbols

@@ -0,0 +1,26 @@
+//// [tests/cases/conformance/types/union/unionTypeCallSignatures7.ts] ////
+
+=== unionTypeCallSignatures7.ts ===
+// https://github.com/microsoft/TypeScript/issues/55203
+
+interface Callable<Name extends string> {
+>Callable : Symbol(Callable, Decl(unionTypeCallSignatures7.ts, 0, 0))
+>Name : Symbol(Name, Decl(unionTypeCallSignatures7.ts, 2, 19))
+
+  (): `${Name} without id`;
+>Name : Symbol(Name, Decl(unionTypeCallSignatures7.ts, 2, 19))
+
+  (id: number): `${Name} with id`;
+>id : Symbol(id, Decl(unionTypeCallSignatures7.ts, 4, 3))
+>Name : Symbol(Name, Decl(unionTypeCallSignatures7.ts, 2, 19))
+}
+
+declare const f: Callable<"A"> | Callable<"B">;
+>f : Symbol(f, Decl(unionTypeCallSignatures7.ts, 7, 13))
+>Callable : Symbol(Callable, Decl(unionTypeCallSignatures7.ts, 0, 0))
+>Callable : Symbol(Callable, Decl(unionTypeCallSignatures7.ts, 0, 0))
+
+const result = f(123);
+>result : Symbol(result, Decl(unionTypeCallSignatures7.ts, 8, 5))
+>f : Symbol(f, Decl(unionTypeCallSignatures7.ts, 7, 13))
+

tests/baselines/reference/unionTypeCallSignatures7.types

@@ -0,0 +1,20 @@
+//// [tests/cases/conformance/types/union/unionTypeCallSignatures7.ts] ////
+
+=== unionTypeCallSignatures7.ts ===
+// https://github.com/microsoft/TypeScript/issues/55203
+
+interface Callable<Name extends string> {
+  (): `${Name} without id`;
+  (id: number): `${Name} with id`;
+>id : number
+}
+
+declare const f: Callable<"A"> | Callable<"B">;
+>f : Callable<"A"> | Callable<"B">
+
+const result = f(123);
+>result : "A with id" | "B with id"
+>f(123) : "A with id" | "B with id"
+>f : Callable<"A"> | Callable<"B">
+>123 : 123
+

tests/cases/conformance/types/union/unionTypeCallSignatures7.ts

@@ -0,0 +1,12 @@
+// @strict: true
+// @noEmit: true
+
+// https://github.com/microsoft/TypeScript/issues/55203
+
+interface Callable<Name extends string> {
+  (): `${Name} without id`;
+  (id: number): `${Name} with id`;
+}
+
+declare const f: Callable<"A"> | Callable<"B">;
+const result = f(123);