use global NaN symbol for NaN equality comparisons

a-tarasyuk · a-tarasyuk · commit 5ca49bb07365 · 2022-09-15T09:07:34.000+03:00
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -996,6 +996,7 @@ namespace ts {
         let deferredGlobalOmitSymbol: Symbol | undefined;
         let deferredGlobalAwaitedSymbol: Symbol | undefined;
         let deferredGlobalBigIntType: ObjectType | undefined;
+        let deferredGlobalNaNSymbol: Symbol | undefined;
 
         const allPotentiallyUnusedIdentifiers = new Map<Path, PotentiallyUnusedIdentifier[]>(); // key is file name
 
@@ -14287,6 +14288,10 @@ namespace ts {
             return (deferredGlobalBigIntType ||= getGlobalType("BigInt" as __String, /*arity*/ 0, /*reportErrors*/ false)) || emptyObjectType;
         }
 
+        function getGlobalNaNSymbol(): Symbol | undefined {
+            return (deferredGlobalNaNSymbol ||= getGlobalValueSymbol("NaN" as __String, /*reportErrors*/ false));
+        }
+
         /**
          * Instantiates a global type that is generic with some element type, and returns that instantiation.
          */
@@ -34386,7 +34391,7 @@ namespace ts {
                         const eqType = operator === SyntaxKind.EqualsEqualsToken || operator === SyntaxKind.EqualsEqualsEqualsToken;
                         error(errorNode, Diagnostics.This_condition_will_always_return_0_since_JavaScript_compares_objects_by_reference_not_value, eqType ? "false" : "true");
                     }
-                    checkNaNEquality(errorNode, operator, left, right, leftType, rightType);
+                    checkNaNEquality(errorNode, operator, left, right);
                     reportOperatorErrorUnless((left, right) => isTypeEqualityComparableTo(left, right) || isTypeEqualityComparableTo(right, left));
                     return booleanType;
 
@@ -34620,9 +34625,9 @@ namespace ts {
                 }
             }
 
-            function checkNaNEquality(errorNode: Node | undefined, operator: SyntaxKind, left: Expression, right: Expression, leftType: Type, rightType: Type) {
-                const isLeftNaN = (leftType.flags & TypeFlags.Number) && isNaN(skipParentheses(left));
-                const isRightNaN = (rightType.flags & TypeFlags.Number) && isNaN(skipParentheses(right));
+            function checkNaNEquality(errorNode: Node | undefined, operator: SyntaxKind, left: Expression, right: Expression) {
+                const isLeftNaN = isGlobalNaN(skipParentheses(left));
+                const isRightNaN = isGlobalNaN(skipParentheses(right));
                 if (isLeftNaN || isRightNaN) {
                     const err = error(errorNode, Diagnostics.This_condition_will_always_return_0,
                         tokenToString(operator === SyntaxKind.EqualsEqualsEqualsToken || operator === SyntaxKind.EqualsEqualsToken ? SyntaxKind.FalseKeyword : SyntaxKind.TrueKeyword));
@@ -34635,8 +34640,12 @@ namespace ts {
                 }
             }
 
-            function isNaN(expr: Expression): boolean {
-                return isIdentifier(expr) && expr.escapedText === "NaN";
+            function isGlobalNaN(expr: Expression): boolean {
+                if (isIdentifier(expr) && expr.escapedText === "NaN") {
+                    const globalNaNSymbol = getGlobalNaNSymbol();
+                    return !!globalNaNSymbol && globalNaNSymbol === getResolvedSymbol(expr);
+                }
+                return false;
             }
         }
 
diff --git a/tests/baselines/reference/nanEquality.errors.txt b/tests/baselines/reference/nanEquality.errors.txt
@@ -94,4 +94,16 @@ tests/cases/compiler/nanEquality.ts(29,5): error TS2845: This condition will alw
         ~~~~~~~~~~~~~~~
 !!! error TS2845: This condition will always return 'false'.
 !!! related TS1369 tests/cases/compiler/nanEquality.ts:29:13: Did you mean 'Number.isNaN(...)'?
+    
+    function t1(value: number, NaN: number) {
+        return value === NaN; // ok
+    }
+    
+    function t2(value: number, NaN: number) {
+        return NaN == value; // ok
+    }
+    
+    function t3(NaN: number) {
+        return NaN === NaN; // ok
+    }
     
diff --git a/tests/baselines/reference/nanEquality.js b/tests/baselines/reference/nanEquality.js
@@ -28,6 +28,18 @@ if (NaN != NaN) {}
 // ...
 declare let y: any;
 if (NaN === y[0][1]) {}
+
+function t1(value: number, NaN: number) {
+    return value === NaN; // ok
+}
+
+function t2(value: number, NaN: number) {
+    return NaN == value; // ok
+}
+
+function t3(NaN: number) {
+    return NaN === NaN; // ok
+}
 
 
 //// [nanEquality.js]
@@ -48,3 +60,12 @@ if (NaN !== NaN) { }
 if (NaN == NaN) { }
 if (NaN != NaN) { }
 if (NaN === y[0][1]) { }
+function t1(value, NaN) {
+    return value === NaN; // ok
+}
+function t2(value, NaN) {
+    return NaN == value; // ok
+}
+function t3(NaN) {
+    return NaN === NaN; // ok
+}
diff --git a/tests/baselines/reference/nanEquality.symbols b/tests/baselines/reference/nanEquality.symbols
@@ -74,3 +74,32 @@ if (NaN === y[0][1]) {}
 >NaN : Symbol(NaN, Decl(lib.es5.d.ts, --, --))
 >y : Symbol(y, Decl(nanEquality.ts, 27, 11))
 
+function t1(value: number, NaN: number) {
+>t1 : Symbol(t1, Decl(nanEquality.ts, 28, 23))
+>value : Symbol(value, Decl(nanEquality.ts, 30, 12))
+>NaN : Symbol(NaN, Decl(nanEquality.ts, 30, 26))
+
+    return value === NaN; // ok
+>value : Symbol(value, Decl(nanEquality.ts, 30, 12))
+>NaN : Symbol(NaN, Decl(nanEquality.ts, 30, 26))
+}
+
+function t2(value: number, NaN: number) {
+>t2 : Symbol(t2, Decl(nanEquality.ts, 32, 1))
+>value : Symbol(value, Decl(nanEquality.ts, 34, 12))
+>NaN : Symbol(NaN, Decl(nanEquality.ts, 34, 26))
+
+    return NaN == value; // ok
+>NaN : Symbol(NaN, Decl(nanEquality.ts, 34, 26))
+>value : Symbol(value, Decl(nanEquality.ts, 34, 12))
+}
+
+function t3(NaN: number) {
+>t3 : Symbol(t3, Decl(nanEquality.ts, 36, 1))
+>NaN : Symbol(NaN, Decl(nanEquality.ts, 38, 12))
+
+    return NaN === NaN; // ok
+>NaN : Symbol(NaN, Decl(nanEquality.ts, 38, 12))
+>NaN : Symbol(NaN, Decl(nanEquality.ts, 38, 12))
+}
+
diff --git a/tests/baselines/reference/nanEquality.types b/tests/baselines/reference/nanEquality.types
@@ -103,3 +103,35 @@ if (NaN === y[0][1]) {}
 >0 : 0
 >1 : 1
 
+function t1(value: number, NaN: number) {
+>t1 : (value: number, NaN: number) => boolean
+>value : number
+>NaN : number
+
+    return value === NaN; // ok
+>value === NaN : boolean
+>value : number
+>NaN : number
+}
+
+function t2(value: number, NaN: number) {
+>t2 : (value: number, NaN: number) => boolean
+>value : number
+>NaN : number
+
+    return NaN == value; // ok
+>NaN == value : boolean
+>NaN : number
+>value : number
+}
+
+function t3(NaN: number) {
+>t3 : (NaN: number) => boolean
+>NaN : number
+
+    return NaN === NaN; // ok
+>NaN === NaN : boolean
+>NaN : number
+>NaN : number
+}
+
diff --git a/tests/cases/compiler/nanEquality.ts b/tests/cases/compiler/nanEquality.ts
@@ -27,3 +27,15 @@ if (NaN != NaN) {}
 // ...
 declare let y: any;
 if (NaN === y[0][1]) {}
+
+function t1(value: number, NaN: number) {
+    return value === NaN; // ok
+}
+
+function t2(value: number, NaN: number) {
+    return NaN == value; // ok
+}
+
+function t3(NaN: number) {
+    return NaN === NaN; // ok
+}
