Fix variable type inference circularity

src/compiler/checker.ts

@@ -16131,7 +16131,7 @@ namespace ts {
         }
 
         function checkDeclarationInitializer(declaration: VariableLikeDeclaration) {
-            const type = checkExpressionCached(declaration.initializer);
+            const type = getTypeOfExpression(declaration.initializer, /*cache*/ true);
             return getCombinedNodeFlags(declaration) & NodeFlags.Const ||
                 getCombinedModifierFlags(declaration) & ModifierFlags.Readonly && !isParameterPropertyDeclaration(declaration) ||
                 isTypeAssertion(declaration.initializer) ? type : getWidenedLiteralType(type);
@@ -16204,10 +16204,12 @@ namespace ts {
 
         // Returns the type of an expression. Unlike checkExpression, this function is simply concerned
         // with computing the type and may not fully check all contained sub-expressions for errors.
-        function getTypeOfExpression(node: Expression) {
+        // A cache argument of true indicates that if the function performs a full type check, it is ok
+        // to cache the result.
+        function getTypeOfExpression(node: Expression, cache?: boolean) {
             // Optimize for the common case of a call to a function with a single non-generic call
             // signature where we can just fetch the return type without checking the arguments.
-            if (node.kind === SyntaxKind.CallExpression && (<CallExpression>node).expression.kind !== SyntaxKind.SuperKeyword) {
+            if (node.kind === SyntaxKind.CallExpression && (<CallExpression>node).expression.kind !== SyntaxKind.SuperKeyword && !isRequireCall(node, /*checkArgumentIsStringLiteral*/true)) {
                 const funcType = checkNonNullExpression((<CallExpression>node).expression);
                 const signature = getSingleCallSignature(funcType);
                 if (signature && !signature.typeParameters) {
@@ -16217,7 +16219,7 @@ namespace ts {
             // Otherwise simply call checkExpression. Ideally, the entire family of checkXXX functions
             // should have a parameter that indicates whether full error checking is required such that
             // we can perform the optimizations locally.
-            return checkExpression(node);
+            return cache ? checkExpressionCached(node) : checkExpression(node);
         }
 
         // Checks an expression and returns its type. The contextualMapper parameter serves two purposes: When

tests/baselines/reference/ambientRequireFunction.types

@@ -3,7 +3,7 @@
 
 const fs = require("fs");
 >fs : typeof "fs"
->require("fs") : any
+>require("fs") : typeof "fs"
 >require : (moduleName: string) => any
 >"fs" : "fs"
 

tests/baselines/reference/circularInferredTypeOfVariable.js

@@ -0,0 +1,44 @@
+//// [circularInferredTypeOfVariable.ts]
+
+// Repro from #14428
+
+(async () => {
+    function foo(p: string[]): string[] {
+        return [];
+    }
+
+    function bar(p: string[]): string[] {
+        return [];
+    }
+
+    let a1: string[] | undefined = [];
+
+    while (true) {
+        let a2 = foo(a1!);
+        a1 = await bar(a2);
+    }
+});
+
+//// [circularInferredTypeOfVariable.js]
+// Repro from #14428
+var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    return new (P || (P = Promise))(function (resolve, reject) {
+        function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
+        function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
+        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        step((generator = generator.apply(thisArg, _arguments || [])).next());
+    });
+};
+(() => __awaiter(this, void 0, void 0, function* () {
+    function foo(p) {
+        return [];
+    }
+    function bar(p) {
+        return [];
+    }
+    let a1 = [];
+    while (true) {
+        let a2 = foo(a1);
+        a1 = yield bar(a2);
+    }
+}));

tests/baselines/reference/circularInferredTypeOfVariable.symbols

@@ -0,0 +1,34 @@
+=== tests/cases/compiler/circularInferredTypeOfVariable.ts ===
+
+// Repro from #14428
+
+(async () => {
+    function foo(p: string[]): string[] {
+>foo : Symbol(foo, Decl(circularInferredTypeOfVariable.ts, 3, 14))
+>p : Symbol(p, Decl(circularInferredTypeOfVariable.ts, 4, 17))
+
+        return [];
+    }
+
+    function bar(p: string[]): string[] {
+>bar : Symbol(bar, Decl(circularInferredTypeOfVariable.ts, 6, 5))
+>p : Symbol(p, Decl(circularInferredTypeOfVariable.ts, 8, 17))
+
+        return [];
+    }
+
+    let a1: string[] | undefined = [];
+>a1 : Symbol(a1, Decl(circularInferredTypeOfVariable.ts, 12, 7))
+
+    while (true) {
+        let a2 = foo(a1!);
+>a2 : Symbol(a2, Decl(circularInferredTypeOfVariable.ts, 15, 11))
+>foo : Symbol(foo, Decl(circularInferredTypeOfVariable.ts, 3, 14))
+>a1 : Symbol(a1, Decl(circularInferredTypeOfVariable.ts, 12, 7))
+
+        a1 = await bar(a2);
+>a1 : Symbol(a1, Decl(circularInferredTypeOfVariable.ts, 12, 7))
+>bar : Symbol(bar, Decl(circularInferredTypeOfVariable.ts, 6, 5))
+>a2 : Symbol(a2, Decl(circularInferredTypeOfVariable.ts, 15, 11))
+    }
+});

tests/baselines/reference/circularInferredTypeOfVariable.types

@@ -0,0 +1,47 @@
+=== tests/cases/compiler/circularInferredTypeOfVariable.ts ===
+
+// Repro from #14428
+
+(async () => {
+>(async () => {    function foo(p: string[]): string[] {        return [];    }    function bar(p: string[]): string[] {        return [];    }    let a1: string[] | undefined = [];    while (true) {        let a2 = foo(a1!);        a1 = await bar(a2);    }}) : () => Promise<never>
+>async () => {    function foo(p: string[]): string[] {        return [];    }    function bar(p: string[]): string[] {        return [];    }    let a1: string[] | undefined = [];    while (true) {        let a2 = foo(a1!);        a1 = await bar(a2);    }} : () => Promise<never>
+
+    function foo(p: string[]): string[] {
+>foo : (p: string[]) => string[]
+>p : string[]
+
+        return [];
+>[] : undefined[]
+    }
+
+    function bar(p: string[]): string[] {
+>bar : (p: string[]) => string[]
+>p : string[]
+
+        return [];
+>[] : undefined[]
+    }
+
+    let a1: string[] | undefined = [];
+>a1 : string[]
+>[] : undefined[]
+
+    while (true) {
+>true : true
+
+        let a2 = foo(a1!);
+>a2 : string[]
+>foo(a1!) : string[]
+>foo : (p: string[]) => string[]
+>a1! : string[]
+>a1 : string[]
+
+        a1 = await bar(a2);
+>a1 = await bar(a2) : string[]
+>a1 : string[]
+>await bar(a2) : string[]
+>bar(a2) : string[]
+>bar : (p: string[]) => string[]
+>a2 : string[]
+    }
+});

tests/baselines/reference/controlFlowIterationErrors.errors.txt

@@ -6,15 +6,9 @@ tests/cases/conformance/controlFlow/controlFlowIterationErrors.ts(35,17): error
   Type 'string' is not assignable to type 'number'.
 tests/cases/conformance/controlFlow/controlFlowIterationErrors.ts(46,17): error TS2345: Argument of type 'string | number' is not assignable to parameter of type 'number'.
   Type 'string' is not assignable to type 'number'.
-tests/cases/conformance/controlFlow/controlFlowIterationErrors.ts(77,13): error TS7022: 'y' implicitly has type 'any' because it does not have a type annotation and is referenced directly or indirectly in its own initializer.
-tests/cases/conformance/controlFlow/controlFlowIterationErrors.ts(77,26): error TS2345: Argument of type 'string | number | boolean' is not assignable to parameter of type 'string | number'.
-  Type 'true' is not assignable to type 'string | number'.
-tests/cases/conformance/controlFlow/controlFlowIterationErrors.ts(88,13): error TS7022: 'y' implicitly has type 'any' because it does not have a type annotation and is referenced directly or indirectly in its own initializer.
-tests/cases/conformance/controlFlow/controlFlowIterationErrors.ts(88,26): error TS2345: Argument of type 'string | number | boolean' is not assignable to parameter of type 'string | number'.
-  Type 'true' is not assignable to type 'string | number'.
 
 
-==== tests/cases/conformance/controlFlow/controlFlowIterationErrors.ts (8 errors) ====
+==== tests/cases/conformance/controlFlow/controlFlowIterationErrors.ts (4 errors) ====
 
     let cond: boolean;
 
@@ -104,11 +98,6 @@ tests/cases/conformance/controlFlow/controlFlowIterationErrors.ts(88,26): error
         x = "0";
         while (cond) {
             let y = asNumber(x);
-                ~
-!!! error TS7022: 'y' implicitly has type 'any' because it does not have a type annotation and is referenced directly or indirectly in its own initializer.
-                             ~
-!!! error TS2345: Argument of type 'string | number | boolean' is not assignable to parameter of type 'string | number'.
-!!! error TS2345:   Type 'true' is not assignable to type 'string | number'.
             x = y + 1;
             x;
         }
@@ -120,11 +109,6 @@ tests/cases/conformance/controlFlow/controlFlowIterationErrors.ts(88,26): error
         while (cond) {
             x;
             let y = asNumber(x);
-                ~
-!!! error TS7022: 'y' implicitly has type 'any' because it does not have a type annotation and is referenced directly or indirectly in its own initializer.
-                             ~
-!!! error TS2345: Argument of type 'string | number | boolean' is not assignable to parameter of type 'string | number'.
-!!! error TS2345:   Type 'true' is not assignable to type 'string | number'.
             x = y + 1;
             x;
         }

tests/baselines/reference/implicitAnyFromCircularInference.errors.txt

@@ -7,11 +7,10 @@ tests/cases/compiler/implicitAnyFromCircularInference.ts(18,10): error TS7024: F
 tests/cases/compiler/implicitAnyFromCircularInference.ts(23,10): error TS7024: Function implicitly has return type 'any' because it does not have a return type annotation and is referenced directly or indirectly in one of its return expressions.
 tests/cases/compiler/implicitAnyFromCircularInference.ts(26,10): error TS7023: 'h' implicitly has return type 'any' because it does not have a return type annotation and is referenced directly or indirectly in one of its return expressions.
 tests/cases/compiler/implicitAnyFromCircularInference.ts(28,14): error TS7023: 'foo' implicitly has return type 'any' because it does not have a return type annotation and is referenced directly or indirectly in one of its return expressions.
-tests/cases/compiler/implicitAnyFromCircularInference.ts(41,5): error TS7022: 's' implicitly has type 'any' because it does not have a type annotation and is referenced directly or indirectly in its own initializer.
 tests/cases/compiler/implicitAnyFromCircularInference.ts(46,9): error TS7023: 'x' implicitly has return type 'any' because it does not have a return type annotation and is referenced directly or indirectly in one of its return expressions.
 
 
-==== tests/cases/compiler/implicitAnyFromCircularInference.ts (11 errors) ====
+==== tests/cases/compiler/implicitAnyFromCircularInference.ts (10 errors) ====
 
     // Error expected
     var a: typeof a;
@@ -71,8 +70,6 @@ tests/cases/compiler/implicitAnyFromCircularInference.ts(46,9): error TS7023: 'x
     class C {
         // Error expected
         s = foo(this);
-        ~~~~~~~~~~~~~~
-!!! error TS7022: 's' implicitly has type 'any' because it does not have a type annotation and is referenced directly or indirectly in its own initializer.
     }
 
     class D {

tests/cases/compiler/circularInferredTypeOfVariable.ts

@@ -0,0 +1,20 @@
+// @target: es6
+
+// Repro from #14428
+
+(async () => {
+    function foo(p: string[]): string[] {
+        return [];
+    }
+
+    function bar(p: string[]): string[] {
+        return [];
+    }
+
+    let a1: string[] | undefined = [];
+
+    while (true) {
+        let a2 = foo(a1!);
+        a1 = await bar(a2);
+    }
+});

tests/cases/fourslash/extendArrayInterfaceMember.ts

@@ -10,7 +10,7 @@ verify.numberOfErrorsInCurrentFile(1);
 // - Supplied parameters do not match any signature of call target.
 // - Could not select overload for 'call' expression.
 
-verify.quickInfoAt("y", "var y: any");
+verify.quickInfoAt("y", "var y: number");
 
 goTo.eof();
 edit.insert("interface Array<T> { pop(def: T): T; }");