Fix creation of composite union type predicates (#54169)

tests/cases/compiler/typePredicatesInUnion3.ts

@@ -0,0 +1,63 @@
+// @strict: true
+// @noEmit: true
+
+// A union of function types is considered a type predicate if at least one constituent is a type
+// predicate and the other constituents are matching type predicates or functions returning `false`.
+
+type P1 = (x: unknown) => x is string;
+type P2 = (x: unknown) => x is number;
+
+type F1 = (x: unknown) => false;
+type F2 = (x: unknown) => boolean;
+type F3 = (x: unknown) => string;
+
+function f1(x: unknown, p: P1 | P2) {
+    if (p(x)) {
+        x;  // string | number
+    }
+}
+
+function f2(x: unknown, p: P1 | P2 | F1) {
+    if (p(x)) {
+        x;  // string | number
+    }
+}
+
+function f3(x: unknown, p: P1 | P2 | F2) {
+    if (p(x)) {
+        x;  // unknown
+    }
+}
+
+function f4(x: unknown, p: P1 | P2 | F3) {
+    if (p(x)) {
+        x;  // unknown
+    }
+}
+
+// Repro from #54143
+
+type HasAttribute<T> = T & { attribute: number };
+
+class Type1 {
+    attribute: number | null = null;
+    predicate(): this is HasAttribute<Type1> {
+        return true;
+    }
+}
+
+class Type2 {
+    attribute: number | null = null;
+    predicate(): boolean {
+        return true;
+    }
+}
+
+function assertType<T>(_val: T) {
+}
+
+declare const val: Type1 | Type2;
+
+if (val.predicate()) {
+    assertType<number>(val.attribute);  // Error
+}