Merge pull request #8390 from Microsoft/narrowingOfDottedNames

Fix narrowing of dotted names

src/compiler/checker.ts

@@ -7335,27 +7335,29 @@ namespace ts {
         }
 
         function containsMatchingReference(source: Node, target: Node) {
-            while (true) {
+            while (source.kind === SyntaxKind.PropertyAccessExpression) {
+                source = (<PropertyAccessExpression>source).expression;
                 if (isMatchingReference(source, target)) {
                     return true;
                 }
-                if (source.kind !== SyntaxKind.PropertyAccessExpression) {
-                    return false;
-                }
-                source = (<PropertyAccessExpression>source).expression;
             }
+            return false;
         }
 
-        function hasMatchingArgument(callExpression: CallExpression, target: Node) {
+        function isOrContainsMatchingReference(source: Node, target: Node) {
+            return isMatchingReference(source, target) || containsMatchingReference(source, target);
+        }
+
+        function hasMatchingArgument(callExpression: CallExpression, reference: Node) {
             if (callExpression.arguments) {
                 for (const argument of callExpression.arguments) {
-                    if (isMatchingReference(argument, target)) {
+                    if (isOrContainsMatchingReference(reference, argument)) {
                         return true;
                     }
                 }
             }
             if (callExpression.expression.kind === SyntaxKind.PropertyAccessExpression &&
-                isMatchingReference((<PropertyAccessExpression>callExpression.expression).expression, target)) {
+                isOrContainsMatchingReference(reference, (<PropertyAccessExpression>callExpression.expression).expression)) {
                 return true;
             }
             return false;
@@ -7618,8 +7620,7 @@ namespace ts {
                 // may be an assignment to a left hand part of the reference. For example, for a
                 // reference 'x.y.z', we may be at an assignment to 'x.y' or 'x'. In that case,
                 // return the declared type.
-                if (reference.kind === SyntaxKind.PropertyAccessExpression &&
-                    containsMatchingReference((<PropertyAccessExpression>reference).expression, node)) {
+                if (containsMatchingReference(reference, node)) {
                     return declaredType;
                 }
                 // Assignment doesn't affect reference
@@ -7682,7 +7683,7 @@ namespace ts {
             }
 
             function narrowTypeByTruthiness(type: Type, expr: Expression, assumeTrue: boolean): Type {
-                return isMatchingReference(expr, reference) ? getTypeWithFacts(type, assumeTrue ? TypeFacts.Truthy : TypeFacts.Falsy) : type;
+                return isMatchingReference(reference, expr) ? getTypeWithFacts(type, assumeTrue ? TypeFacts.Truthy : TypeFacts.Falsy) : type;
             }
 
             function narrowTypeByBinaryExpression(type: Type, expr: BinaryExpression, assumeTrue: boolean): Type {
@@ -7714,7 +7715,7 @@ namespace ts {
                 if (operator === SyntaxKind.ExclamationEqualsToken || operator === SyntaxKind.ExclamationEqualsEqualsToken) {
                     assumeTrue = !assumeTrue;
                 }
-                if (!strictNullChecks || !isMatchingReference(expr.left, reference)) {
+                if (!strictNullChecks || !isMatchingReference(reference, expr.left)) {
                     return type;
                 }
                 const doubleEquals = operator === SyntaxKind.EqualsEqualsToken || operator === SyntaxKind.ExclamationEqualsToken;
@@ -7731,7 +7732,12 @@ namespace ts {
                 // and string literal on the right
                 const left = <TypeOfExpression>expr.left;
                 const right = <LiteralExpression>expr.right;
-                if (!isMatchingReference(left.expression, reference)) {
+                if (!isMatchingReference(reference, left.expression)) {
+                    // For a reference of the form 'x.y', a 'typeof x === ...' type guard resets the
+                    // narrowed type of 'y' to its declared type.
+                    if (containsMatchingReference(reference, left.expression)) {
+                        return declaredType;
+                    }
                     return type;
                 }
                 if (expr.operatorToken.kind === SyntaxKind.ExclamationEqualsToken ||
@@ -7754,8 +7760,16 @@ namespace ts {
             }
 
             function narrowTypeByInstanceof(type: Type, expr: BinaryExpression, assumeTrue: boolean): Type {
-                // Check that type is not any, assumed result is true, and we have variable symbol on the left
-                if (isTypeAny(type) || !isMatchingReference(expr.left, reference)) {
+                if (!isMatchingReference(reference, expr.left)) {
+                    // For a reference of the form 'x.y', an 'x instanceof T' type guard resets the
+                    // narrowed type of 'y' to its declared type.
+                    if (containsMatchingReference(reference, expr.left)) {
+                        return declaredType;
+                    }
+                    return type;
+                }
+                // We never narrow type any in an instanceof guard
+                if (isTypeAny(type)) {
                     return type;
                 }
 
@@ -7830,18 +7844,26 @@ namespace ts {
                 }
                 if (isIdentifierTypePredicate(predicate)) {
                     const predicateArgument = callExpression.arguments[predicate.parameterIndex];
-                    if (predicateArgument && isMatchingReference(predicateArgument, reference)) {
-                        return getNarrowedType(type, predicate.type, assumeTrue);
+                    if (predicateArgument) {
+                        if (isMatchingReference(reference, predicateArgument)) {
+                            return getNarrowedType(type, predicate.type, assumeTrue);
+                        }
+                        if (containsMatchingReference(reference, predicateArgument)) {
+                            return declaredType;
+                        }
                     }
                 }
                 else {
                     const invokedExpression = skipParenthesizedNodes(callExpression.expression);
                     if (invokedExpression.kind === SyntaxKind.ElementAccessExpression || invokedExpression.kind === SyntaxKind.PropertyAccessExpression) {
                         const accessExpression = invokedExpression as ElementAccessExpression | PropertyAccessExpression;
-                        const possibleReference= skipParenthesizedNodes(accessExpression.expression);
-                        if (isMatchingReference(possibleReference, reference)) {
+                        const possibleReference = skipParenthesizedNodes(accessExpression.expression);
+                        if (isMatchingReference(reference, possibleReference)) {
                             return getNarrowedType(type, predicate.type, assumeTrue);
                         }
+                        if (containsMatchingReference(reference, possibleReference)) {
+                            return declaredType;
+                        }
                     }
                 }
                 return type;

tests/baselines/reference/narrowingOfDottedNames.js

@@ -0,0 +1,80 @@
+//// [narrowingOfDottedNames.ts]
+// Repro from #8383
+
+class A {
+    prop: { a: string; };
+}
+
+class B {
+    prop: { b: string; }
+}
+
+function isA(x: any): x is A {
+    return x instanceof A;
+}
+
+function isB(x: any): x is B {
+    return x instanceof B;
+}
+
+function f1(x: A | B) {
+    while (true) {
+        if (x instanceof A) {
+            x.prop.a;
+        }
+        else if (x instanceof B) {
+            x.prop.b;
+        }
+    }
+}
+
+function f2(x: A | B) {
+    while (true) {
+        if (isA(x)) {
+            x.prop.a;
+        }
+        else if (isB(x)) {
+            x.prop.b;
+        }
+    }
+}
+
+
+//// [narrowingOfDottedNames.js]
+// Repro from #8383
+var A = (function () {
+    function A() {
+    }
+    return A;
+}());
+var B = (function () {
+    function B() {
+    }
+    return B;
+}());
+function isA(x) {
+    return x instanceof A;
+}
+function isB(x) {
+    return x instanceof B;
+}
+function f1(x) {
+    while (true) {
+        if (x instanceof A) {
+            x.prop.a;
+        }
+        else if (x instanceof B) {
+            x.prop.b;
+        }
+    }
+}
+function f2(x) {
+    while (true) {
+        if (isA(x)) {
+            x.prop.a;
+        }
+        else if (isB(x)) {
+            x.prop.b;
+        }
+    }
+}

tests/baselines/reference/narrowingOfDottedNames.symbols

@@ -0,0 +1,105 @@
+=== tests/cases/compiler/narrowingOfDottedNames.ts ===
+// Repro from #8383
+
+class A {
+>A : Symbol(A, Decl(narrowingOfDottedNames.ts, 0, 0))
+
+    prop: { a: string; };
+>prop : Symbol(A.prop, Decl(narrowingOfDottedNames.ts, 2, 9))
+>a : Symbol(a, Decl(narrowingOfDottedNames.ts, 3, 11))
+}
+
+class B {
+>B : Symbol(B, Decl(narrowingOfDottedNames.ts, 4, 1))
+
+    prop: { b: string; }
+>prop : Symbol(B.prop, Decl(narrowingOfDottedNames.ts, 6, 9))
+>b : Symbol(b, Decl(narrowingOfDottedNames.ts, 7, 11))
+}
+
+function isA(x: any): x is A {
+>isA : Symbol(isA, Decl(narrowingOfDottedNames.ts, 8, 1))
+>x : Symbol(x, Decl(narrowingOfDottedNames.ts, 10, 13))
+>x : Symbol(x, Decl(narrowingOfDottedNames.ts, 10, 13))
+>A : Symbol(A, Decl(narrowingOfDottedNames.ts, 0, 0))
+
+    return x instanceof A;
+>x : Symbol(x, Decl(narrowingOfDottedNames.ts, 10, 13))
+>A : Symbol(A, Decl(narrowingOfDottedNames.ts, 0, 0))
+}
+
+function isB(x: any): x is B {
+>isB : Symbol(isB, Decl(narrowingOfDottedNames.ts, 12, 1))
+>x : Symbol(x, Decl(narrowingOfDottedNames.ts, 14, 13))
+>x : Symbol(x, Decl(narrowingOfDottedNames.ts, 14, 13))
+>B : Symbol(B, Decl(narrowingOfDottedNames.ts, 4, 1))
+
+    return x instanceof B;
+>x : Symbol(x, Decl(narrowingOfDottedNames.ts, 14, 13))
+>B : Symbol(B, Decl(narrowingOfDottedNames.ts, 4, 1))
+}
+
+function f1(x: A | B) {
+>f1 : Symbol(f1, Decl(narrowingOfDottedNames.ts, 16, 1))
+>x : Symbol(x, Decl(narrowingOfDottedNames.ts, 18, 12))
+>A : Symbol(A, Decl(narrowingOfDottedNames.ts, 0, 0))
+>B : Symbol(B, Decl(narrowingOfDottedNames.ts, 4, 1))
+
+    while (true) {
+        if (x instanceof A) {
+>x : Symbol(x, Decl(narrowingOfDottedNames.ts, 18, 12))
+>A : Symbol(A, Decl(narrowingOfDottedNames.ts, 0, 0))
+
+            x.prop.a;
+>x.prop.a : Symbol(a, Decl(narrowingOfDottedNames.ts, 3, 11))
+>x.prop : Symbol(A.prop, Decl(narrowingOfDottedNames.ts, 2, 9))
+>x : Symbol(x, Decl(narrowingOfDottedNames.ts, 18, 12))
+>prop : Symbol(A.prop, Decl(narrowingOfDottedNames.ts, 2, 9))
+>a : Symbol(a, Decl(narrowingOfDottedNames.ts, 3, 11))
+        }
+        else if (x instanceof B) {
+>x : Symbol(x, Decl(narrowingOfDottedNames.ts, 18, 12))
+>B : Symbol(B, Decl(narrowingOfDottedNames.ts, 4, 1))
+
+            x.prop.b;
+>x.prop.b : Symbol(b, Decl(narrowingOfDottedNames.ts, 7, 11))
+>x.prop : Symbol(B.prop, Decl(narrowingOfDottedNames.ts, 6, 9))
+>x : Symbol(x, Decl(narrowingOfDottedNames.ts, 18, 12))
+>prop : Symbol(B.prop, Decl(narrowingOfDottedNames.ts, 6, 9))
+>b : Symbol(b, Decl(narrowingOfDottedNames.ts, 7, 11))
+        }
+    }
+}
+
+function f2(x: A | B) {
+>f2 : Symbol(f2, Decl(narrowingOfDottedNames.ts, 27, 1))
+>x : Symbol(x, Decl(narrowingOfDottedNames.ts, 29, 12))
+>A : Symbol(A, Decl(narrowingOfDottedNames.ts, 0, 0))
+>B : Symbol(B, Decl(narrowingOfDottedNames.ts, 4, 1))
+
+    while (true) {
+        if (isA(x)) {
+>isA : Symbol(isA, Decl(narrowingOfDottedNames.ts, 8, 1))
+>x : Symbol(x, Decl(narrowingOfDottedNames.ts, 29, 12))
+
+            x.prop.a;
+>x.prop.a : Symbol(a, Decl(narrowingOfDottedNames.ts, 3, 11))
+>x.prop : Symbol(A.prop, Decl(narrowingOfDottedNames.ts, 2, 9))
+>x : Symbol(x, Decl(narrowingOfDottedNames.ts, 29, 12))
+>prop : Symbol(A.prop, Decl(narrowingOfDottedNames.ts, 2, 9))
+>a : Symbol(a, Decl(narrowingOfDottedNames.ts, 3, 11))
+        }
+        else if (isB(x)) {
+>isB : Symbol(isB, Decl(narrowingOfDottedNames.ts, 12, 1))
+>x : Symbol(x, Decl(narrowingOfDottedNames.ts, 29, 12))
+
+            x.prop.b;
+>x.prop.b : Symbol(b, Decl(narrowingOfDottedNames.ts, 7, 11))
+>x.prop : Symbol(B.prop, Decl(narrowingOfDottedNames.ts, 6, 9))
+>x : Symbol(x, Decl(narrowingOfDottedNames.ts, 29, 12))
+>prop : Symbol(B.prop, Decl(narrowingOfDottedNames.ts, 6, 9))
+>b : Symbol(b, Decl(narrowingOfDottedNames.ts, 7, 11))
+        }
+    }
+}
+

tests/baselines/reference/narrowingOfDottedNames.types

@@ -0,0 +1,115 @@
+=== tests/cases/compiler/narrowingOfDottedNames.ts ===
+// Repro from #8383
+
+class A {
+>A : A
+
+    prop: { a: string; };
+>prop : { a: string; }
+>a : string
+}
+
+class B {
+>B : B
+
+    prop: { b: string; }
+>prop : { b: string; }
+>b : string
+}
+
+function isA(x: any): x is A {
+>isA : (x: any) => x is A
+>x : any
+>x : any
+>A : A
+
+    return x instanceof A;
+>x instanceof A : boolean
+>x : any
+>A : typeof A
+}
+
+function isB(x: any): x is B {
+>isB : (x: any) => x is B
+>x : any
+>x : any
+>B : B
+
+    return x instanceof B;
+>x instanceof B : boolean
+>x : any
+>B : typeof B
+}
+
+function f1(x: A | B) {
+>f1 : (x: A | B) => void
+>x : A | B
+>A : A
+>B : B
+
+    while (true) {
+>true : boolean
+
+        if (x instanceof A) {
+>x instanceof A : boolean
+>x : A | B
+>A : typeof A
+
+            x.prop.a;
+>x.prop.a : string
+>x.prop : { a: string; }
+>x : A
+>prop : { a: string; }
+>a : string
+        }
+        else if (x instanceof B) {
+>x instanceof B : boolean
+>x : B
+>B : typeof B
+
+            x.prop.b;
+>x.prop.b : string
+>x.prop : { b: string; }
+>x : B
+>prop : { b: string; }
+>b : string
+        }
+    }
+}
+
+function f2(x: A | B) {
+>f2 : (x: A | B) => void
+>x : A | B
+>A : A
+>B : B
+
+    while (true) {
+>true : boolean
+
+        if (isA(x)) {
+>isA(x) : boolean
+>isA : (x: any) => x is A
+>x : A | B
+
+            x.prop.a;
+>x.prop.a : string
+>x.prop : { a: string; }
+>x : A
+>prop : { a: string; }
+>a : string
+        }
+        else if (isB(x)) {
+>isB(x) : boolean
+>isB : (x: any) => x is B
+>x : B
+
+            x.prop.b;
+>x.prop.b : string
+>x.prop : { b: string; }
+>x : B
+>prop : { b: string; }
+>b : string
+        }
+    }
+}
+

tests/cases/compiler/narrowingOfDottedNames.ts

@@ -0,0 +1,39 @@
+// Repro from #8383
+
+class A {
+    prop: { a: string; };
+}
+
+class B {
+    prop: { b: string; }
+}
+
+function isA(x: any): x is A {
+    return x instanceof A;
+}
+
+function isB(x: any): x is B {
+    return x instanceof B;
+}
+
+function f1(x: A | B) {
+    while (true) {
+        if (x instanceof A) {
+            x.prop.a;
+        }
+        else if (x instanceof B) {
+            x.prop.b;
+        }
+    }
+}
+
+function f2(x: A | B) {
+    while (true) {
+        if (isA(x)) {
+            x.prop.a;
+        }
+        else if (isB(x)) {
+            x.prop.b;
+        }
+    }
+}