Allow indirect calls (#51989)

Co-authored-by: Klaus Meinhardt <klaus.meinhardt1@gmail.com>

src/compiler/checker.ts

@@ -35810,7 +35810,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                     return getRegularTypeOfObjectLiteral(rightType);
                 }
             case SyntaxKind.CommaToken:
-                if (!compilerOptions.allowUnreachableCode && isSideEffectFree(left) && !isEvalNode(right)) {
+                if (!compilerOptions.allowUnreachableCode && isSideEffectFree(left) && !isIndirectCall(left.parent as BinaryExpression)) {
                     const sf = getSourceFileOfNode(left);
                     const sourceText = sf.text;
                     const start = skipTrivia(sourceText, left.pos);
@@ -35846,8 +35846,14 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             }
         }
 
-        function isEvalNode(node: Expression) {
-            return node.kind === SyntaxKind.Identifier && (node as Identifier).escapedText === "eval";
+        // Return true for "indirect calls", (i.e. `(0, x.f)(...)` or `(0, eval)(...)`), which prevents passing `this`.
+        function isIndirectCall(node: BinaryExpression): boolean {
+            return node.parent.kind === SyntaxKind.ParenthesizedExpression &&
+                isNumericLiteral(node.left) &&
+                node.left.text === "0" &&
+                (isCallExpression(node.parent.parent) && node.parent.parent.expression === node.parent || node.parent.parent.kind === SyntaxKind.TaggedTemplateExpression) &&
+                // special-case for "eval" because it's the only non-access case where an indirect call actually affects behavior.
+                (isAccessExpression(node.right) || isIdentifier(node.right) && node.right.escapedText === "eval");
         }
 
         // Return true if there was no error, false if there was an error.

tests/baselines/reference/commaOperatorLeftSideUnused.errors.txt

@@ -21,9 +21,10 @@ tests/cases/compiler/commaOperatorLeftSideUnused.ts(38,7): error TS2695: Left si
 tests/cases/compiler/commaOperatorLeftSideUnused.ts(39,7): error TS2695: Left side of comma operator is unused and has no side effects.
 tests/cases/compiler/commaOperatorLeftSideUnused.ts(40,7): error TS2695: Left side of comma operator is unused and has no side effects.
 tests/cases/compiler/commaOperatorLeftSideUnused.ts(41,7): error TS2695: Left side of comma operator is unused and has no side effects.
+tests/cases/compiler/commaOperatorLeftSideUnused.ts(42,7): error TS2695: Left side of comma operator is unused and has no side effects.
 
 
-==== tests/cases/compiler/commaOperatorLeftSideUnused.ts (23 errors) ====
+==== tests/cases/compiler/commaOperatorLeftSideUnused.ts (24 errors) ====
     var xx: any;
     var yy: any;
     
@@ -111,6 +112,9 @@ tests/cases/compiler/commaOperatorLeftSideUnused.ts(41,7): error TS2695: Left si
     xx = (+xx, 10);
           ~~~
 !!! error TS2695: Left side of comma operator is unused and has no side effects.
+    xx = (0, xx)();
+          ~
+!!! error TS2695: Left side of comma operator is unused and has no side effects.
     
     // OK cases
     xx = (xx ? x++ : 4, 10);
@@ -122,4 +126,6 @@ tests/cases/compiler/commaOperatorLeftSideUnused.ts(41,7): error TS2695: Left si
     xx = (Math.pow(3, 2), 4);
     xx = (void xx, 10);
     xx = (xx as any, 100);
-    
+    xx = (0, xx.fn)();
+    xx = (0, xx['fn'])();
+    xx = (0, xx.fn)``;

tests/baselines/reference/commaOperatorLeftSideUnused.js

@@ -40,6 +40,7 @@ xx = (!xx, 10);
 xx = (~xx, 10);
 xx = (-xx, 10);
 xx = (+xx, 10);
+xx = (0, xx)();
 
 // OK cases
 xx = (xx ? x++ : 4, 10);
@@ -51,9 +52,15 @@ xx = ((xx+= 4), xx);
 xx = (Math.pow(3, 2), 4);
 xx = (void xx, 10);
 xx = (xx as any, 100);
-
+xx = (0, xx.fn)();
+xx = (0, xx['fn'])();
+xx = (0, xx.fn)``;
 
 //// [commaOperatorLeftSideUnused.js]
+var __makeTemplateObject = (this && this.__makeTemplateObject) || function (cooked, raw) {
+    if (Object.defineProperty) { Object.defineProperty(cooked, "raw", { value: raw }); } else { cooked.raw = raw; }
+    return cooked;
+};
 var xx;
 var yy;
 function fn() {
@@ -91,6 +98,7 @@ xx = (!xx, 10);
 xx = (~xx, 10);
 xx = (-xx, 10);
 xx = (+xx, 10);
+xx = (0, xx)();
 // OK cases
 xx = (xx ? x++ : 4, 10);
 xx = (--xx, 3);
@@ -101,3 +109,6 @@ xx = ((xx += 4), xx);
 xx = (Math.pow(3, 2), 4);
 xx = (void xx, 10);
 xx = (xx, 100);
+xx = (0, xx.fn)();
+xx = (0, xx['fn'])();
+xx = (0, xx.fn)(__makeTemplateObject([""], [""]));

tests/baselines/reference/commaOperatorLeftSideUnused.symbols

@@ -109,6 +109,10 @@ xx = (+xx, 10);
 >xx : Symbol(xx, Decl(commaOperatorLeftSideUnused.ts, 0, 3))
 >xx : Symbol(xx, Decl(commaOperatorLeftSideUnused.ts, 0, 3))
 
+xx = (0, xx)();
+>xx : Symbol(xx, Decl(commaOperatorLeftSideUnused.ts, 0, 3))
+>xx : Symbol(xx, Decl(commaOperatorLeftSideUnused.ts, 0, 3))
+
 // OK cases
 xx = (xx ? x++ : 4, 10);
 >xx : Symbol(xx, Decl(commaOperatorLeftSideUnused.ts, 0, 3))
@@ -151,3 +155,15 @@ xx = (xx as any, 100);
 >xx : Symbol(xx, Decl(commaOperatorLeftSideUnused.ts, 0, 3))
 >xx : Symbol(xx, Decl(commaOperatorLeftSideUnused.ts, 0, 3))
 
+xx = (0, xx.fn)();
+>xx : Symbol(xx, Decl(commaOperatorLeftSideUnused.ts, 0, 3))
+>xx : Symbol(xx, Decl(commaOperatorLeftSideUnused.ts, 0, 3))
+
+xx = (0, xx['fn'])();
+>xx : Symbol(xx, Decl(commaOperatorLeftSideUnused.ts, 0, 3))
+>xx : Symbol(xx, Decl(commaOperatorLeftSideUnused.ts, 0, 3))
+
+xx = (0, xx.fn)``;
+>xx : Symbol(xx, Decl(commaOperatorLeftSideUnused.ts, 0, 3))
+>xx : Symbol(xx, Decl(commaOperatorLeftSideUnused.ts, 0, 3))
+

tests/baselines/reference/commaOperatorLeftSideUnused.types

@@ -240,6 +240,15 @@ xx = (+xx, 10);
 >xx : any
 >10 : 10
 
+xx = (0, xx)();
+>xx = (0, xx)() : any
+>xx : any
+>(0, xx)() : any
+>(0, xx) : any
+>0, xx : any
+>0 : 0
+>xx : any
+
 // OK cases
 xx = (xx ? x++ : 4, 10);
 >xx = (xx ? x++ : 4, 10) : 10
@@ -335,3 +344,37 @@ xx = (xx as any, 100);
 >xx : any
 >100 : 100
 
+xx = (0, xx.fn)();
+>xx = (0, xx.fn)() : any
+>xx : any
+>(0, xx.fn)() : any
+>(0, xx.fn) : any
+>0, xx.fn : any
+>0 : 0
+>xx.fn : any
+>xx : any
+>fn : any
+
+xx = (0, xx['fn'])();
+>xx = (0, xx['fn'])() : any
+>xx : any
+>(0, xx['fn'])() : any
+>(0, xx['fn']) : any
+>0, xx['fn'] : any
+>0 : 0
+>xx['fn'] : any
+>xx : any
+>'fn' : "fn"
+
+xx = (0, xx.fn)``;
+>xx = (0, xx.fn)`` : any
+>xx : any
+>(0, xx.fn)`` : any
+>(0, xx.fn) : any
+>0, xx.fn : any
+>0 : 0
+>xx.fn : any
+>xx : any
+>fn : any
+>`` : ""
+

tests/cases/compiler/commaOperatorLeftSideUnused.ts

@@ -40,6 +40,7 @@ xx = (!xx, 10);
 xx = (~xx, 10);
 xx = (-xx, 10);
 xx = (+xx, 10);
+xx = (0, xx)();
 
 // OK cases
 xx = (xx ? x++ : 4, 10);
@@ -51,3 +52,6 @@ xx = ((xx+= 4), xx);
 xx = (Math.pow(3, 2), 4);
 xx = (void xx, 10);
 xx = (xx as any, 100);
+xx = (0, xx.fn)();
+xx = (0, xx['fn'])();
+xx = (0, xx.fn)``;