A second attempt at readonly array support persisting through isArray

microsoft · Jan 13, 2021 · 6cd8141 · 6cd8141
1 parent a894f8a
commit 6cd8141
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Showing 8 changed files with 48 additions and 37 deletions.
diff --git a/lib/lib.es5.d.ts b/lib/lib.es5.d.ts
@@ -1408,7 +1408,7 @@ interface ArrayConstructor {
     (arrayLength?: number): any[];
     <T>(arrayLength: number): T[];
     <T>(...items: T[]): T[];
-    isArray(arg: any): arg is any[];
+    isArray(arg: any): arg is readonly unknown[];
     readonly prototype: any[];
 }
 

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -22999,11 +22999,16 @@ namespace ts {
                     }
                 }
 
-                // If the candidate type is a subtype of the target type, narrow to the candidate type,
-                // if the target type is a subtype of the candidate type, narrow to the target type,
-                // otherwise, narrow to an intersection of the two types.
-                return isTypeSubtypeOf(candidate, type) ? candidate : isTypeSubtypeOf(type, candidate) ? type : getIntersectionType([type, candidate]);
-            }
+                 // If the candidate type is a subtype of the target type, narrow to the candidate type.
+                 // Otherwise, if the target type is assignable to the candidate type, keep the target type.
+                 // Otherwise, if the candidate type is assignable to the target type, narrow to the candidate
+                 // type. Otherwise, the types are completely unrelated, so narrow to an intersection of the
+                 // two types.
+                 return isTypeSubtypeOf(candidate, type) ? candidate :
+                     isTypeAssignableTo(type, candidate) ? type :
+                     isTypeAssignableTo(candidate, type) ? candidate :
+                     getIntersectionType([type, candidate]);
+                }
 
             function narrowTypeByCallExpression(type: Type, callExpression: CallExpression, assumeTrue: boolean): Type {
                 if (hasMatchingArgument(callExpression, reference)) {

diff --git a/tests/baselines/reference/instanceOfAssignability.types b/tests/baselines/reference/instanceOfAssignability.types
@@ -70,8 +70,8 @@ function fn2(x: Base) {
 		// 1.5: y: Base
 		// Want: y: Derived1
 		let y = x;
->y : Base & Derived1
->x : Base & Derived1
+>y : Derived1
+>x : Derived1
 	}
 }
 
@@ -104,8 +104,8 @@ function fn4(x: Base|Derived2) {
 		// 1.5: y: {}
 		// Want: Derived1
 		let y = x;
->y : (Base | Derived2) & Derived1
->x : (Base | Derived2) & Derived1
+>y : Derived1
+>x : Derived1
 	}
 }
 

diff --git a/tests/baselines/reference/typeGuardIntersectionTypes.symbols b/tests/baselines/reference/typeGuardIntersectionTypes.symbols
@@ -176,37 +176,37 @@ function identifyBeast(beast: Beast) {
 >beast : Symbol(beast, Decl(typeGuardIntersectionTypes.ts, 64, 23))
 
             if (beast.legs === 4) {
->beast.legs : Symbol(legs, Decl(typeGuardIntersectionTypes.ts, 55, 38), Decl(typeGuardIntersectionTypes.ts, 56, 21))
+>beast.legs : Symbol(Legged.legs, Decl(typeGuardIntersectionTypes.ts, 56, 21))
 >beast : Symbol(beast, Decl(typeGuardIntersectionTypes.ts, 64, 23))
->legs : Symbol(legs, Decl(typeGuardIntersectionTypes.ts, 55, 38), Decl(typeGuardIntersectionTypes.ts, 56, 21))
+>legs : Symbol(Legged.legs, Decl(typeGuardIntersectionTypes.ts, 56, 21))
 
                 log(`pegasus - 4 legs, wings`);
 >log : Symbol(log, Decl(typeGuardIntersectionTypes.ts, 48, 1))
             }
             else if (beast.legs === 2) {
->beast.legs : Symbol(legs, Decl(typeGuardIntersectionTypes.ts, 55, 38), Decl(typeGuardIntersectionTypes.ts, 56, 21))
+>beast.legs : Symbol(Legged.legs, Decl(typeGuardIntersectionTypes.ts, 56, 21))
 >beast : Symbol(beast, Decl(typeGuardIntersectionTypes.ts, 64, 23))
->legs : Symbol(legs, Decl(typeGuardIntersectionTypes.ts, 55, 38), Decl(typeGuardIntersectionTypes.ts, 56, 21))
+>legs : Symbol(Legged.legs, Decl(typeGuardIntersectionTypes.ts, 56, 21))
 
                 log(`bird - 2 legs, wings`);
 >log : Symbol(log, Decl(typeGuardIntersectionTypes.ts, 48, 1))
             }
             else {
                 log(`unknown - ${beast.legs} legs, wings`);
 >log : Symbol(log, Decl(typeGuardIntersectionTypes.ts, 48, 1))
->beast.legs : Symbol(legs, Decl(typeGuardIntersectionTypes.ts, 55, 38), Decl(typeGuardIntersectionTypes.ts, 56, 21))
+>beast.legs : Symbol(Legged.legs, Decl(typeGuardIntersectionTypes.ts, 56, 21))
 >beast : Symbol(beast, Decl(typeGuardIntersectionTypes.ts, 64, 23))
->legs : Symbol(legs, Decl(typeGuardIntersectionTypes.ts, 55, 38), Decl(typeGuardIntersectionTypes.ts, 56, 21))
+>legs : Symbol(Legged.legs, Decl(typeGuardIntersectionTypes.ts, 56, 21))
             }
         }
 
         // All non-winged beasts with legs
         else {
             log(`manbearpig - ${beast.legs} legs, no wings`);
 >log : Symbol(log, Decl(typeGuardIntersectionTypes.ts, 48, 1))
->beast.legs : Symbol(legs, Decl(typeGuardIntersectionTypes.ts, 55, 38), Decl(typeGuardIntersectionTypes.ts, 56, 21))
+>beast.legs : Symbol(Legged.legs, Decl(typeGuardIntersectionTypes.ts, 56, 21))
 >beast : Symbol(beast, Decl(typeGuardIntersectionTypes.ts, 64, 23))
->legs : Symbol(legs, Decl(typeGuardIntersectionTypes.ts, 55, 38), Decl(typeGuardIntersectionTypes.ts, 56, 21))
+>legs : Symbol(Legged.legs, Decl(typeGuardIntersectionTypes.ts, 56, 21))
         }
     }
 

diff --git a/tests/baselines/reference/typeGuardIntersectionTypes.types b/tests/baselines/reference/typeGuardIntersectionTypes.types
@@ -166,12 +166,12 @@ function identifyBeast(beast: Beast) {
         if (hasWings(beast)) {
 >hasWings(beast) : boolean
 >hasWings : (x: Beast) => x is Winged
->beast : Beast & Legged
+>beast : Legged
 
             if (beast.legs === 4) {
 >beast.legs === 4 : boolean
 >beast.legs : number
->beast : Beast & Legged & Winged
+>beast : Legged & Winged
 >legs : number
 >4 : 4
 
@@ -183,7 +183,7 @@ function identifyBeast(beast: Beast) {
             else if (beast.legs === 2) {
 >beast.legs === 2 : boolean
 >beast.legs : number
->beast : Beast & Legged & Winged
+>beast : Legged & Winged
 >legs : number
 >2 : 2
 
@@ -198,7 +198,7 @@ function identifyBeast(beast: Beast) {
 >log : (s: string) => void
 >`unknown - ${beast.legs} legs, wings` : `unknown - ${number} legs, wings`
 >beast.legs : number
->beast : Beast & Legged & Winged
+>beast : Legged & Winged
 >legs : number
             }
         }
@@ -210,7 +210,7 @@ function identifyBeast(beast: Beast) {
 >log : (s: string) => void
 >`manbearpig - ${beast.legs} legs, no wings` : `manbearpig - ${number} legs, no wings`
 >beast.legs : number
->beast : Beast & Legged
+>beast : Legged
 >legs : number
         }
     }

diff --git a/tests/baselines/reference/typeGuardsWithInstanceOf.errors.txt b/tests/baselines/reference/typeGuardsWithInstanceOf.errors.txt
@@ -1,8 +1,12 @@
 tests/cases/conformance/expressions/typeGuards/typeGuardsWithInstanceOf.ts(7,20): error TS2339: Property 'global' does not exist on type 'never'.
   The intersection 'I & RegExp' was reduced to 'never' because property 'global' has conflicting types in some constituents.
+tests/cases/conformance/expressions/typeGuards/typeGuardsWithInstanceOf.ts(31,11): error TS2339: Property 'onChanges' does not exist on type 'C | (Validator & Partial<OnChanges>)'.
+  Property 'onChanges' does not exist on type 'C'.
+tests/cases/conformance/expressions/typeGuards/typeGuardsWithInstanceOf.ts(32,11): error TS2339: Property 'onChanges' does not exist on type 'C | (Validator & Partial<OnChanges>)'.
+  Property 'onChanges' does not exist on type 'C'.
 
 
-==== tests/cases/conformance/expressions/typeGuards/typeGuardsWithInstanceOf.ts (1 errors) ====
+==== tests/cases/conformance/expressions/typeGuards/typeGuardsWithInstanceOf.ts (3 errors) ====
     interface I { global: string; }
     var result!: I;
     var result2!: I;
@@ -37,7 +41,13 @@ tests/cases/conformance/expressions/typeGuards/typeGuardsWithInstanceOf.ts(7,20)
         }
         v // Validator & Partial<OnChanges> via subtype reduction
         if (v.onChanges) {
+              ~~~~~~~~~
+!!! error TS2339: Property 'onChanges' does not exist on type 'C | (Validator & Partial<OnChanges>)'.
+!!! error TS2339:   Property 'onChanges' does not exist on type 'C'.
             v.onChanges({});
+              ~~~~~~~~~
+!!! error TS2339: Property 'onChanges' does not exist on type 'C | (Validator & Partial<OnChanges>)'.
+!!! error TS2339:   Property 'onChanges' does not exist on type 'C'.
         }
     }
 

diff --git a/tests/baselines/reference/typeGuardsWithInstanceOf.symbols b/tests/baselines/reference/typeGuardsWithInstanceOf.symbols
@@ -71,14 +71,10 @@ function foo() {
 >v : Symbol(v, Decl(typeGuardsWithInstanceOf.ts, 25, 7))
 
     if (v.onChanges) {
->v.onChanges : Symbol(onChanges, Decl(typeGuardsWithInstanceOf.ts, 11, 21))
 >v : Symbol(v, Decl(typeGuardsWithInstanceOf.ts, 25, 7))
->onChanges : Symbol(onChanges, Decl(typeGuardsWithInstanceOf.ts, 11, 21))
 
         v.onChanges({});
->v.onChanges : Symbol(onChanges, Decl(typeGuardsWithInstanceOf.ts, 11, 21))
 >v : Symbol(v, Decl(typeGuardsWithInstanceOf.ts, 25, 7))
->onChanges : Symbol(onChanges, Decl(typeGuardsWithInstanceOf.ts, 11, 21))
     }
 }
 

diff --git a/tests/baselines/reference/typeGuardsWithInstanceOf.types b/tests/baselines/reference/typeGuardsWithInstanceOf.types
@@ -65,21 +65,21 @@ function foo() {
 >C : typeof C
 
         v // Validator & Partial<OnChanges> & C
->v : Validator & Partial<OnChanges> & C
+>v : C
     }
     v // Validator & Partial<OnChanges> via subtype reduction
->v : Validator & Partial<OnChanges>
+>v : C | (Validator & Partial<OnChanges>)
 
     if (v.onChanges) {
->v.onChanges : ((changes: Record<string, unknown>) => void) | undefined
->v : Validator & Partial<OnChanges>
->onChanges : ((changes: Record<string, unknown>) => void) | undefined
+>v.onChanges : any
+>v : C | (Validator & Partial<OnChanges>)
+>onChanges : any
 
         v.onChanges({});
->v.onChanges({}) : void
->v.onChanges : (changes: Record<string, unknown>) => void
->v : Validator & Partial<OnChanges>
->onChanges : (changes: Record<string, unknown>) => void
+>v.onChanges({}) : any
+>v.onChanges : any
+>v : C | (Validator & Partial<OnChanges>)
+>onChanges : any
 >{} : {}
     }
 }