Don’t error for missing await when promise is referenced in condition body (#43593)

Author: andrewbranch

src/compiler/checker.ts

@@ -35371,15 +35371,6 @@ namespace ts {
             if (!strictNullChecks) return;
             if (getFalsyFlags(type)) return;
 
-            if (getAwaitedTypeOfPromise(type)) {
-                errorAndMaybeSuggestAwait(
-                    condExpr,
-                    /*maybeMissingAwait*/ true,
-                    Diagnostics.This_condition_will_always_return_true_since_this_0_appears_to_always_be_defined,
-                    getTypeNameForErrorDisplay(type));
-                return;
-            }
-
             const location = isBinaryExpression(condExpr) ? condExpr.right : condExpr;
             const testedNode = isIdentifier(location) ? location
                 : isPropertyAccessExpression(location) ? location.name
@@ -35392,12 +35383,13 @@ namespace ts {
             }
 
             // While it technically should be invalid for any known-truthy value
-            // to be tested, we de-scope to functions unrefenced in the block as a
-            // heuristic to identify the most common bugs. There are too many
-            // false positives for values sourced from type definitions without
-            // strictNullChecks otherwise.
+            // to be tested, we de-scope to functions and Promises unreferenced in
+            // the block as a heuristic to identify the most common bugs. There
+            // are too many false positives for values sourced from type
+            // definitions without strictNullChecks otherwise.
             const callSignatures = getSignaturesOfType(type, SignatureKind.Call);
-            if (callSignatures.length === 0) {
+            const isPromise = !!getAwaitedTypeOfPromise(type);
+            if (callSignatures.length === 0 && !isPromise) {
                 return;
             }
 
@@ -35406,14 +35398,23 @@ namespace ts {
                 return;
             }
 
-            const isUsed = isBinaryExpression(condExpr.parent) && isFunctionUsedInBinaryExpressionChain(condExpr.parent, testedSymbol)
-                || body && isFunctionUsedInConditionBody(condExpr, body, testedNode, testedSymbol);
+            const isUsed = isBinaryExpression(condExpr.parent) && isSymbolUsedInBinaryExpressionChain(condExpr.parent, testedSymbol)
+                || body && isSymbolUsedInConditionBody(condExpr, body, testedNode, testedSymbol);
             if (!isUsed) {
-                error(location, Diagnostics.This_condition_will_always_return_true_since_this_function_appears_to_always_be_defined_Did_you_mean_to_call_it_instead);
+                if (isPromise) {
+                    errorAndMaybeSuggestAwait(
+                        location,
+                        /*maybeMissingAwait*/ true,
+                        Diagnostics.This_condition_will_always_return_true_since_this_0_is_always_defined,
+                        getTypeNameForErrorDisplay(type));
+                }
+                else {
+                    error(location, Diagnostics.This_condition_will_always_return_true_since_this_function_is_always_defined_Did_you_mean_to_call_it_instead);
+                }
             }
         }
 
-        function isFunctionUsedInConditionBody(expr: Expression, body: Statement | Expression, testedNode: Node, testedSymbol: Symbol): boolean {
+        function isSymbolUsedInConditionBody(expr: Expression, body: Statement | Expression, testedNode: Node, testedSymbol: Symbol): boolean {
             return !!forEachChild(body, function check(childNode): boolean | undefined {
                 if (isIdentifier(childNode)) {
                     const childSymbol = getSymbolAtLocation(childNode);
@@ -35451,7 +35452,7 @@ namespace ts {
             });
         }
 
-        function isFunctionUsedInBinaryExpressionChain(node: Node, testedSymbol: Symbol): boolean {
+        function isSymbolUsedInBinaryExpressionChain(node: Node, testedSymbol: Symbol): boolean {
             while (isBinaryExpression(node) && node.operatorToken.kind === SyntaxKind.AmpersandAmpersandToken) {
                 const isUsed = forEachChild(node.right, function visit(child): boolean | undefined {
                     if (isIdentifier(child)) {

src/compiler/diagnosticMessages.json

@@ -3172,7 +3172,7 @@
         "category": "Error",
         "code": 2773
     },
-    "This condition will always return true since this function appears to always be defined. Did you mean to call it instead?": {
+    "This condition will always return true since this function is always defined. Did you mean to call it instead?": {
         "category": "Error",
         "code": 2774
     },
@@ -3280,7 +3280,7 @@
         "category": "Error",
         "code": 2800
     },
-    "This condition will always return true since this '{0}' appears to always be defined.": {
+    "This condition will always return true since this '{0}' is always defined.": {
         "category": "Error",
         "code": 2801
     },

src/services/codefixes/addMissingAwait.ts

@@ -14,7 +14,7 @@ namespace ts.codefix {
         Diagnostics.Operator_0_cannot_be_applied_to_type_1.code,
         Diagnostics.Operator_0_cannot_be_applied_to_types_1_and_2.code,
         Diagnostics.This_condition_will_always_return_0_since_the_types_1_and_2_have_no_overlap.code,
-        Diagnostics.This_condition_will_always_return_true_since_this_0_appears_to_always_be_defined.code,
+        Diagnostics.This_condition_will_always_return_true_since_this_0_is_always_defined.code,
         Diagnostics.Type_0_is_not_an_array_type.code,
         Diagnostics.Type_0_is_not_an_array_type_or_a_string_type.code,
         Diagnostics.Type_0_is_not_an_array_type_or_a_string_type_Use_compiler_option_downlevelIteration_to_allow_iterating_of_iterators.code,

src/services/codefixes/fixMissingCallParentheses.ts

@@ -2,7 +2,7 @@
 namespace ts.codefix {
     const fixId = "fixMissingCallParentheses";
     const errorCodes = [
-        Diagnostics.This_condition_will_always_return_true_since_this_function_appears_to_always_be_defined_Did_you_mean_to_call_it_instead.code,
+        Diagnostics.This_condition_will_always_return_true_since_this_function_is_always_defined_Did_you_mean_to_call_it_instead.code,
     ];
 
     registerCodeFix({

tests/baselines/reference/truthinessCallExpressionCoercion.errors.txt

@@ -1,17 +1,17 @@
-tests/cases/compiler/truthinessCallExpressionCoercion.ts(2,9): error TS2774: This condition will always return true since this function appears to always be defined. Did you mean to call it instead?
-tests/cases/compiler/truthinessCallExpressionCoercion.ts(18,9): error TS2774: This condition will always return true since this function appears to always be defined. Did you mean to call it instead?
-tests/cases/compiler/truthinessCallExpressionCoercion.ts(36,9): error TS2774: This condition will always return true since this function appears to always be defined. Did you mean to call it instead?
-tests/cases/compiler/truthinessCallExpressionCoercion.ts(50,9): error TS2774: This condition will always return true since this function appears to always be defined. Did you mean to call it instead?
-tests/cases/compiler/truthinessCallExpressionCoercion.ts(66,13): error TS2774: This condition will always return true since this function appears to always be defined. Did you mean to call it instead?
-tests/cases/compiler/truthinessCallExpressionCoercion.ts(76,9): error TS2774: This condition will always return true since this function appears to always be defined. Did you mean to call it instead?
-tests/cases/compiler/truthinessCallExpressionCoercion.ts(82,9): error TS2774: This condition will always return true since this function appears to always be defined. Did you mean to call it instead?
+tests/cases/compiler/truthinessCallExpressionCoercion.ts(2,9): error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
+tests/cases/compiler/truthinessCallExpressionCoercion.ts(18,9): error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
+tests/cases/compiler/truthinessCallExpressionCoercion.ts(36,9): error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
+tests/cases/compiler/truthinessCallExpressionCoercion.ts(50,9): error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
+tests/cases/compiler/truthinessCallExpressionCoercion.ts(66,13): error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
+tests/cases/compiler/truthinessCallExpressionCoercion.ts(76,9): error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
+tests/cases/compiler/truthinessCallExpressionCoercion.ts(82,9): error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
 
 
 ==== tests/cases/compiler/truthinessCallExpressionCoercion.ts (7 errors) ====
     function onlyErrorsWhenTestingNonNullableFunctionType(required: () => boolean, optional?: () => boolean) {
         if (required) { // error
             ~~~~~~~~
-!!! error TS2774: This condition will always return true since this function appears to always be defined. Did you mean to call it instead?
+!!! error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
         }
 
         if (optional) { // ok
@@ -29,7 +29,7 @@ tests/cases/compiler/truthinessCallExpressionCoercion.ts(82,9): error TS2774: Th
 
         if (test) { // error
             ~~~~
-!!! error TS2774: This condition will always return true since this function appears to always be defined. Did you mean to call it instead?
+!!! error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
             console.log('test');
         }
 
@@ -49,7 +49,7 @@ tests/cases/compiler/truthinessCallExpressionCoercion.ts(82,9): error TS2774: Th
 
         if (test) { // error
             ~~~~
-!!! error TS2774: This condition will always return true since this function appears to always be defined. Did you mean to call it instead?
+!!! error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
             [() => null].forEach(test => {
                 test();
             });
@@ -65,7 +65,7 @@ tests/cases/compiler/truthinessCallExpressionCoercion.ts(82,9): error TS2774: Th
 
         if (x.foo.bar) { // error
             ~~~~~~~~~
-!!! error TS2774: This condition will always return true since this function appears to always be defined. Did you mean to call it instead?
+!!! error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
         }
 
         if (x.foo.bar) { // ok
@@ -83,7 +83,7 @@ tests/cases/compiler/truthinessCallExpressionCoercion.ts(82,9): error TS2774: Th
         test() {
             if (this.isUser) { // error
                 ~~~~~~~~~~~
-!!! error TS2774: This condition will always return true since this function appears to always be defined. Did you mean to call it instead?
+!!! error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
             }
 
             if (this.maybeIsUser) { // ok
@@ -95,15 +95,15 @@ tests/cases/compiler/truthinessCallExpressionCoercion.ts(82,9): error TS2774: Th
     function A(stats: StatsBase<any>) {
         if (stats.isDirectory) { // err
             ~~~~~~~~~~~~~~~~~
-!!! error TS2774: This condition will always return true since this function appears to always be defined. Did you mean to call it instead?
+!!! error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
             console.log(`[Directory] ${stats.ctime}`)
         }
     }
 
     function B(a: Nested, b: Nested) {
         if (a.stats.isDirectory) { // err
             ~~~~~~~~~~~~~~~~~~~
-!!! error TS2774: This condition will always return true since this function appears to always be defined. Did you mean to call it instead?
+!!! error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
             b.stats.isDirectory(); 
         }
         if (a.stats.isDirectory) { // ok

tests/baselines/reference/truthinessCallExpressionCoercion1.errors.txt

@@ -1,16 +1,16 @@
-tests/cases/compiler/truthinessCallExpressionCoercion1.ts(3,5): error TS2774: This condition will always return true since this function appears to always be defined. Did you mean to call it instead?
-tests/cases/compiler/truthinessCallExpressionCoercion1.ts(19,5): error TS2774: This condition will always return true since this function appears to always be defined. Did you mean to call it instead?
-tests/cases/compiler/truthinessCallExpressionCoercion1.ts(33,5): error TS2774: This condition will always return true since this function appears to always be defined. Did you mean to call it instead?
-tests/cases/compiler/truthinessCallExpressionCoercion1.ts(46,5): error TS2774: This condition will always return true since this function appears to always be defined. Did you mean to call it instead?
-tests/cases/compiler/truthinessCallExpressionCoercion1.ts(76,9): error TS2774: This condition will always return true since this function appears to always be defined. Did you mean to call it instead?
+tests/cases/compiler/truthinessCallExpressionCoercion1.ts(3,5): error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
+tests/cases/compiler/truthinessCallExpressionCoercion1.ts(19,5): error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
+tests/cases/compiler/truthinessCallExpressionCoercion1.ts(33,5): error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
+tests/cases/compiler/truthinessCallExpressionCoercion1.ts(46,5): error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
+tests/cases/compiler/truthinessCallExpressionCoercion1.ts(76,9): error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
 
 
 ==== tests/cases/compiler/truthinessCallExpressionCoercion1.ts (5 errors) ====
     function onlyErrorsWhenTestingNonNullableFunctionType(required: () => boolean, optional?: () => boolean) {
         // error
         required ? console.log('required') : undefined;
         ~~~~~~~~
-!!! error TS2774: This condition will always return true since this function appears to always be defined. Did you mean to call it instead?
+!!! error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
 
         // ok
         optional ? console.log('optional') : undefined;
@@ -28,7 +28,7 @@ tests/cases/compiler/truthinessCallExpressionCoercion1.ts(76,9): error TS2774: T
         // error
         test ? console.log('test') : undefined;
         ~~~~
-!!! error TS2774: This condition will always return true since this function appears to always be defined. Did you mean to call it instead?
+!!! error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
 
         // ok
         test ? console.log(test) : undefined;
@@ -44,7 +44,7 @@ tests/cases/compiler/truthinessCallExpressionCoercion1.ts(76,9): error TS2774: T
         // error
         test
         ~~~~
-!!! error TS2774: This condition will always return true since this function appears to always be defined. Did you mean to call it instead?
+!!! error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
             ? [() => null].forEach(test => { test() })
             : undefined;
     }
@@ -59,7 +59,7 @@ tests/cases/compiler/truthinessCallExpressionCoercion1.ts(76,9): error TS2774: T
         // error
         x.foo.bar ? console.log('x.foo.bar') : undefined;
         ~~~~~~~~~
-!!! error TS2774: This condition will always return true since this function appears to always be defined. Did you mean to call it instead?
+!!! error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
 
         // ok
         x.foo.bar ? x.foo.bar : undefined;
@@ -91,7 +91,7 @@ tests/cases/compiler/truthinessCallExpressionCoercion1.ts(76,9): error TS2774: T
             // error
             this.isUser ? console.log('this.isUser') : undefined;
             ~~~~~~~~~~~
-!!! error TS2774: This condition will always return true since this function appears to always be defined. Did you mean to call it instead?
+!!! error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
 
             // ok
             this.maybeIsUser ? console.log('this.maybeIsUser') : undefined;