Merge pull request #15320 from Microsoft/fixTypePredicateThisParameter

Fix type predicates with this parameters

Author: mhegazy

src/compiler/checker.ts

@@ -11565,7 +11565,7 @@ namespace ts {
                 }
 
                 if (isIdentifierTypePredicate(predicate)) {
-                    const predicateArgument = callExpression.arguments[predicate.parameterIndex];
+                    const predicateArgument = callExpression.arguments[predicate.parameterIndex - (signature.thisParameter ? 1 : 0)];
                     if (predicateArgument) {
                         if (isMatchingReference(reference, predicateArgument)) {
                             return getNarrowedType(type, predicate.type, assumeTrue, isTypeSubtypeOf);

tests/baselines/reference/typePredicateWithThisParameter.js

@@ -0,0 +1,43 @@
+//// [typePredicateWithThisParameter.ts]
+// Repro from #15310
+
+interface Foo {
+    foo: string;
+}
+interface Bar {
+    bar: string;
+}
+
+function isFoo1(object: {}): object is Foo {
+    return 'foo' in object;
+}
+
+function isFoo2(this: void, object: {}): object is Foo {
+    return 'foo' in object;
+}
+
+declare let test: Foo | Bar;
+
+if (isFoo1(test)) {
+    test.foo = 'hi';
+}
+
+if (isFoo2(test)) {
+    test.foo = 'hi';
+}
+
+
+//// [typePredicateWithThisParameter.js]
+// Repro from #15310
+function isFoo1(object) {
+    return 'foo' in object;
+}
+function isFoo2(object) {
+    return 'foo' in object;
+}
+if (isFoo1(test)) {
+    test.foo = 'hi';
+}
+if (isFoo2(test)) {
+    test.foo = 'hi';
+}

tests/baselines/reference/typePredicateWithThisParameter.symbols

@@ -0,0 +1,62 @@
+=== tests/cases/compiler/typePredicateWithThisParameter.ts ===
+// Repro from #15310
+
+interface Foo {
+>Foo : Symbol(Foo, Decl(typePredicateWithThisParameter.ts, 0, 0))
+
+    foo: string;
+>foo : Symbol(Foo.foo, Decl(typePredicateWithThisParameter.ts, 2, 15))
+}
+interface Bar {
+>Bar : Symbol(Bar, Decl(typePredicateWithThisParameter.ts, 4, 1))
+
+    bar: string;
+>bar : Symbol(Bar.bar, Decl(typePredicateWithThisParameter.ts, 5, 15))
+}
+
+function isFoo1(object: {}): object is Foo {
+>isFoo1 : Symbol(isFoo1, Decl(typePredicateWithThisParameter.ts, 7, 1))
+>object : Symbol(object, Decl(typePredicateWithThisParameter.ts, 9, 16))
+>object : Symbol(object, Decl(typePredicateWithThisParameter.ts, 9, 16))
+>Foo : Symbol(Foo, Decl(typePredicateWithThisParameter.ts, 0, 0))
+
+    return 'foo' in object;
+>object : Symbol(object, Decl(typePredicateWithThisParameter.ts, 9, 16))
+}
+
+function isFoo2(this: void, object: {}): object is Foo {
+>isFoo2 : Symbol(isFoo2, Decl(typePredicateWithThisParameter.ts, 11, 1))
+>this : Symbol(this, Decl(typePredicateWithThisParameter.ts, 13, 16))
+>object : Symbol(object, Decl(typePredicateWithThisParameter.ts, 13, 27))
+>object : Symbol(object, Decl(typePredicateWithThisParameter.ts, 13, 27))
+>Foo : Symbol(Foo, Decl(typePredicateWithThisParameter.ts, 0, 0))
+
+    return 'foo' in object;
+>object : Symbol(object, Decl(typePredicateWithThisParameter.ts, 13, 27))
+}
+
+declare let test: Foo | Bar;
+>test : Symbol(test, Decl(typePredicateWithThisParameter.ts, 17, 11))
+>Foo : Symbol(Foo, Decl(typePredicateWithThisParameter.ts, 0, 0))
+>Bar : Symbol(Bar, Decl(typePredicateWithThisParameter.ts, 4, 1))
+
+if (isFoo1(test)) {
+>isFoo1 : Symbol(isFoo1, Decl(typePredicateWithThisParameter.ts, 7, 1))
+>test : Symbol(test, Decl(typePredicateWithThisParameter.ts, 17, 11))
+
+    test.foo = 'hi';
+>test.foo : Symbol(Foo.foo, Decl(typePredicateWithThisParameter.ts, 2, 15))
+>test : Symbol(test, Decl(typePredicateWithThisParameter.ts, 17, 11))
+>foo : Symbol(Foo.foo, Decl(typePredicateWithThisParameter.ts, 2, 15))
+}
+
+if (isFoo2(test)) {
+>isFoo2 : Symbol(isFoo2, Decl(typePredicateWithThisParameter.ts, 11, 1))
+>test : Symbol(test, Decl(typePredicateWithThisParameter.ts, 17, 11))
+
+    test.foo = 'hi';
+>test.foo : Symbol(Foo.foo, Decl(typePredicateWithThisParameter.ts, 2, 15))
+>test : Symbol(test, Decl(typePredicateWithThisParameter.ts, 17, 11))
+>foo : Symbol(Foo.foo, Decl(typePredicateWithThisParameter.ts, 2, 15))
+}
+

tests/baselines/reference/typePredicateWithThisParameter.types

@@ -0,0 +1,72 @@
+=== tests/cases/compiler/typePredicateWithThisParameter.ts ===
+// Repro from #15310
+
+interface Foo {
+>Foo : Foo
+
+    foo: string;
+>foo : string
+}
+interface Bar {
+>Bar : Bar
+
+    bar: string;
+>bar : string
+}
+
+function isFoo1(object: {}): object is Foo {
+>isFoo1 : (object: {}) => object is Foo
+>object : {}
+>object : any
+>Foo : Foo
+
+    return 'foo' in object;
+>'foo' in object : boolean
+>'foo' : "foo"
+>object : {}
+}
+
+function isFoo2(this: void, object: {}): object is Foo {
+>isFoo2 : (this: void, object: {}) => object is Foo
+>this : void
+>object : {}
+>object : any
+>Foo : Foo
+
+    return 'foo' in object;
+>'foo' in object : boolean
+>'foo' : "foo"
+>object : {}
+}
+
+declare let test: Foo | Bar;
+>test : Foo | Bar
+>Foo : Foo
+>Bar : Bar
+
+if (isFoo1(test)) {
+>isFoo1(test) : boolean
+>isFoo1 : (object: {}) => object is Foo
+>test : Foo | Bar
+
+    test.foo = 'hi';
+>test.foo = 'hi' : "hi"
+>test.foo : string
+>test : Foo
+>foo : string
+>'hi' : "hi"
+}
+
+if (isFoo2(test)) {
+>isFoo2(test) : boolean
+>isFoo2 : (this: void, object: {}) => object is Foo
+>test : Foo | Bar
+
+    test.foo = 'hi';
+>test.foo = 'hi' : "hi"
+>test.foo : string
+>test : Foo
+>foo : string
+>'hi' : "hi"
+}
+

tests/cases/compiler/typePredicateWithThisParameter.ts

@@ -0,0 +1,26 @@
+// Repro from #15310
+
+interface Foo {
+    foo: string;
+}
+interface Bar {
+    bar: string;
+}
+
+function isFoo1(object: {}): object is Foo {
+    return 'foo' in object;
+}
+
+function isFoo2(this: void, object: {}): object is Foo {
+    return 'foo' in object;
+}
+
+declare let test: Foo | Bar;
+
+if (isFoo1(test)) {
+    test.foo = 'hi';
+}
+
+if (isFoo2(test)) {
+    test.foo = 'hi';
+}