Do not classify Infinity and NaN (microsoft#44778)

* Do not classify Infinity and NaN. Fixes microsoft#42022

* Internally expose so that the classifier can use it

* Increase the test complexity, and revert the type-checker

* Drop the -Infinity

Co-authored-by: Orta <[email protected]>

Author: jeanp413

src/services/classifier2020.ts

@@ -79,7 +79,7 @@ namespace ts.classifier.v2020 {
                 inJSXElement = false;
             }
 
-            if (isIdentifier(node) && !inJSXElement && !inImportClause(node)) {
+            if (isIdentifier(node) && !inJSXElement && !inImportClause(node) && !isInfinityOrNaNString(node.escapedText)) {
                 let symbol = typeChecker.getSymbolAtLocation(node);
                 if (symbol) {
                     if (symbol.flags & SymbolFlags.Alias) {
@@ -225,6 +225,10 @@ namespace ts.classifier.v2020 {
         return (isQualifiedName(node.parent) && node.parent.right === node) || (isPropertyAccessExpression(node.parent) && node.parent.name === node);
     }
 
+    function isInfinityOrNaNString(name: __String): boolean {
+        return name === "Infinity" || name === "NaN";
+    }
+
     const tokenFromDeclarationMapping = new Map<SyntaxKind, TokenType>([
         [SyntaxKind.VariableDeclaration, TokenType.variable],
         [SyntaxKind.Parameter, TokenType.parameter],

tests/cases/fourslash/semanticModernClassificationInfinityAndNaN.ts

@@ -0,0 +1,39 @@
+/// <reference path="fourslash.ts"/>
+
+//// Infinity;
+//// NaN;
+////
+////// Regular properties
+////
+////const obj1 = {
+////    Infinity: 100,
+////    NaN: 200,
+////    "-Infinity": 300
+////};
+////
+////obj1.Infinity;
+////obj1.NaN;
+////obj1["-Infinity"];
+////
+////// Shorthand properties
+////
+////const obj2 = {
+////    Infinity,
+////    NaN,
+////}
+////
+////obj2.Infinity;
+////obj2.NaN;
+
+// Basically only the obj1 and obj2 should be showing up in this list
+
+const c2 = classification("2020");
+verify.semanticClassificationsAre("2020",
+    c2.semanticToken("variable.declaration.readonly", "obj1"), 
+    c2.semanticToken("variable.readonly", "obj1"), 
+    c2.semanticToken("variable.readonly", "obj1"), 
+    c2.semanticToken("variable.readonly", "obj1"), 
+    c2.semanticToken("variable.declaration.readonly", "obj2"), 
+    c2.semanticToken("variable.readonly", "obj2"), 
+    c2.semanticToken("variable.readonly", "obj2"), 
+);