Enable CFA on this keyword unconditionally (#21490)

Author: weswigham

src/compiler/checker.ts

@@ -13341,13 +13341,13 @@ namespace ts {
                         .expression;                             // x
                     const classSymbol = checkExpression(className).symbol;
                     if (classSymbol && classSymbol.members && (classSymbol.flags & SymbolFlags.Function)) {
-                        return getInferredClassType(classSymbol);
+                        return getFlowTypeOfReference(node, getInferredClassType(classSymbol));
                     }
                 }
 
                 const thisType = getThisTypeOfDeclaration(container) || getContextualThisParameterType(container);
                 if (thisType) {
-                    return thisType;
+                    return getFlowTypeOfReference(node, thisType);
                 }
             }
 
@@ -13360,7 +13360,7 @@ namespace ts {
             if (isInJavaScriptFile(node)) {
                 const type = getTypeForThisExpressionFromJSDoc(container);
                 if (type && type !== unknownType) {
-                    return type;
+                    return getFlowTypeOfReference(node, type);
                 }
             }
         }

tests/baselines/reference/controlFlowAnalysisOnBareThisKeyword.js

@@ -0,0 +1,26 @@
+//// [controlFlowAnalysisOnBareThisKeyword.ts]
+declare function isBig(x: any): x is { big: true };
+function bigger(this: {}) {
+    if (isBig(this)) {
+        this.big; // Expect property to exist
+    }
+}
+
+function bar(this: string | number) {
+    if (typeof this === "string") {
+        const x: string = this;
+    }
+}
+
+//// [controlFlowAnalysisOnBareThisKeyword.js]
+"use strict";
+function bigger() {
+    if (isBig(this)) {
+        this.big; // Expect property to exist
+    }
+}
+function bar() {
+    if (typeof this === "string") {
+        var x = this;
+    }
+}

tests/baselines/reference/controlFlowAnalysisOnBareThisKeyword.symbols

@@ -0,0 +1,34 @@
+=== tests/cases/compiler/controlFlowAnalysisOnBareThisKeyword.ts ===
+declare function isBig(x: any): x is { big: true };
+>isBig : Symbol(isBig, Decl(controlFlowAnalysisOnBareThisKeyword.ts, 0, 0))
+>x : Symbol(x, Decl(controlFlowAnalysisOnBareThisKeyword.ts, 0, 23))
+>x : Symbol(x, Decl(controlFlowAnalysisOnBareThisKeyword.ts, 0, 23))
+>big : Symbol(big, Decl(controlFlowAnalysisOnBareThisKeyword.ts, 0, 38))
+
+function bigger(this: {}) {
+>bigger : Symbol(bigger, Decl(controlFlowAnalysisOnBareThisKeyword.ts, 0, 51))
+>this : Symbol(this, Decl(controlFlowAnalysisOnBareThisKeyword.ts, 1, 16))
+
+    if (isBig(this)) {
+>isBig : Symbol(isBig, Decl(controlFlowAnalysisOnBareThisKeyword.ts, 0, 0))
+>this : Symbol(this, Decl(controlFlowAnalysisOnBareThisKeyword.ts, 1, 16))
+
+        this.big; // Expect property to exist
+>this.big : Symbol(big, Decl(controlFlowAnalysisOnBareThisKeyword.ts, 0, 38))
+>this : Symbol(this, Decl(controlFlowAnalysisOnBareThisKeyword.ts, 1, 16))
+>big : Symbol(big, Decl(controlFlowAnalysisOnBareThisKeyword.ts, 0, 38))
+    }
+}
+
+function bar(this: string | number) {
+>bar : Symbol(bar, Decl(controlFlowAnalysisOnBareThisKeyword.ts, 5, 1))
+>this : Symbol(this, Decl(controlFlowAnalysisOnBareThisKeyword.ts, 7, 13))
+
+    if (typeof this === "string") {
+>this : Symbol(this, Decl(controlFlowAnalysisOnBareThisKeyword.ts, 7, 13))
+
+        const x: string = this;
+>x : Symbol(x, Decl(controlFlowAnalysisOnBareThisKeyword.ts, 9, 13))
+>this : Symbol(this, Decl(controlFlowAnalysisOnBareThisKeyword.ts, 7, 13))
+    }
+}

tests/baselines/reference/controlFlowAnalysisOnBareThisKeyword.types

@@ -0,0 +1,39 @@
+=== tests/cases/compiler/controlFlowAnalysisOnBareThisKeyword.ts ===
+declare function isBig(x: any): x is { big: true };
+>isBig : (x: any) => x is { big: true; }
+>x : any
+>x : any
+>big : true
+>true : true
+
+function bigger(this: {}) {
+>bigger : (this: {}) => void
+>this : {}
+
+    if (isBig(this)) {
+>isBig(this) : boolean
+>isBig : (x: any) => x is { big: true; }
+>this : {}
+
+        this.big; // Expect property to exist
+>this.big : true
+>this : { big: true; }
+>big : true
+    }
+}
+
+function bar(this: string | number) {
+>bar : (this: string | number) => void
+>this : string | number
+
+    if (typeof this === "string") {
+>typeof this === "string" : boolean
+>typeof this : "string" | "number" | "boolean" | "symbol" | "undefined" | "object" | "function"
+>this : string | number
+>"string" : "string"
+
+        const x: string = this;
+>x : string
+>this : string
+    }
+}

tests/cases/compiler/controlFlowAnalysisOnBareThisKeyword.ts

@@ -0,0 +1,13 @@
+// @strict: true
+declare function isBig(x: any): x is { big: true };
+function bigger(this: {}) {
+    if (isBig(this)) {
+        this.big; // Expect property to exist
+    }
+}
+
+function bar(this: string | number) {
+    if (typeof this === "string") {
+        const x: string = this;
+    }
+}