fix #16702: polish type predicate error message

Author: HerringtonDarkholme

src/compiler/checker.ts

@@ -8517,7 +8517,7 @@ namespace ts {
                     }
                     else if (isIdentifierTypePredicate(target.typePredicate)) {
                         if (reportErrors) {
-                            errorReporter(Diagnostics.Signature_0_must_have_a_type_predicate, signatureToString(source));
+                            errorReporter(Diagnostics.Signature_0_must_be_a_type_predicate, signatureToString(source));
                         }
                         return Ternary.False;
                     }

src/compiler/diagnosticMessages.json

@@ -707,7 +707,7 @@
         "category": "Error",
         "code": 1223
     },
-    "Signature '{0}' must have a type predicate.": {
+    "Signature '{0}' must be a type predicate.": {
         "category": "Error",
         "code": 1224
     },
@@ -3637,7 +3637,7 @@
         "category": "Message",
         "code": 90025
     },
-    
+
     "Convert function to an ES2015 class": {
         "category": "Message",
         "code": 95001

tests/baselines/reference/typeGuardFunctionErrors.errors.txt

@@ -27,7 +27,7 @@ tests/cases/conformance/expressions/typeGuards/typeGuardFunctionErrors.ts(74,46)
     Type 'C' is not assignable to type 'B'.
       Property 'propB' is missing in type 'C'.
 tests/cases/conformance/expressions/typeGuards/typeGuardFunctionErrors.ts(78,1): error TS2322: Type '(p1: any, p2: any) => boolean' is not assignable to type '(p1: any, p2: any) => p1 is A'.
-  Signature '(p1: any, p2: any): boolean' must have a type predicate.
+  Signature '(p1: any, p2: any): boolean' must be a type predicate.
 tests/cases/conformance/expressions/typeGuards/typeGuardFunctionErrors.ts(84,1): error TS2322: Type '(p1: any, p2: any) => p2 is A' is not assignable to type '(p1: any, p2: any) => p1 is A'.
   Type predicate 'p2 is A' is not assignable to 'p1 is A'.
     Parameter 'p2' is not in the same position as parameter 'p1'.
@@ -194,7 +194,7 @@ tests/cases/conformance/expressions/typeGuards/typeGuardFunctionErrors.ts(136,39
     assign1 = function(p1, p2): boolean {
     ~~~~~~~
 !!! error TS2322: Type '(p1: any, p2: any) => boolean' is not assignable to type '(p1: any, p2: any) => p1 is A'.
-!!! error TS2322:   Signature '(p1: any, p2: any): boolean' must have a type predicate.
+!!! error TS2322:   Signature '(p1: any, p2: any): boolean' must be a type predicate.
         return true;
     };