Port TypeScript#63070: Be more lenient about iteration when lib=es5 / noLib

internal/checker/checker.go

@@ -5919,7 +5919,8 @@ func (c *Checker) getIteratedTypeOrElementType(use IterationUse, inputType *Type
 		return nil
 	}
 	// TODO: remove ScriptTargetES2015
-	uplevelIteration := c.languageVersion >= core.ScriptTargetES2015
+	iterableExists := c.getGlobalIterableType() != c.emptyGenericType
+	uplevelIteration := c.languageVersion >= core.ScriptTargetES2015 && iterableExists
 	downlevelIteration := !uplevelIteration && c.compilerOptions.DownlevelIteration == core.TSTrue
 	possibleOutOfBounds := c.compilerOptions.NoUncheckedIndexedAccess == core.TSTrue && use&IterationUsePossiblyOutOfBounds != 0
 	// Get the iterated type of an `Iterable<T>` or `IterableIterator<T>` only in ES2015

testdata/baselines/reference/submodule/compiler/arrayIterationLibES5TargetDifferent(nolib=false,target=es2015).errors.txt

@@ -1,38 +1,32 @@
-arrayIterationLibES5TargetDifferent.ts(3,17): error TS2488: Type 'number[]' must have a '[Symbol.iterator]()' method that returns an iterator.
-arrayIterationLibES5TargetDifferent.ts(9,17): error TS2488: Type 'string' must have a '[Symbol.iterator]()' method that returns an iterator.
-arrayIterationLibES5TargetDifferent.ts(15,17): error TS2488: Type 'number' must have a '[Symbol.iterator]()' method that returns an iterator.
-arrayIterationLibES5TargetDifferent.ts(21,17): error TS2488: Type '{ foo: string; }' must have a '[Symbol.iterator]()' method that returns an iterator.
+arrayIterationLibES5TargetDifferent.ts(15,17): error TS2495: Type 'number' is not an array type or a string type.
+arrayIterationLibES5TargetDifferent.ts(21,17): error TS2495: Type '{ foo: string; }' is not an array type or a string type.
 
 
-==== arrayIterationLibES5TargetDifferent.ts (4 errors) ====
+==== arrayIterationLibES5TargetDifferent.ts (2 errors) ====
     declare function log(message?: any): void;
 
     for (const x of [1, 2, 3]) {
-                    ~~~~~~~~~
-!!! error TS2488: Type 'number[]' must have a '[Symbol.iterator]()' method that returns an iterator.
         log(x);
     }
 
     declare const aString: string;
 
     for (const x of aString) {
-                    ~~~~~~~
-!!! error TS2488: Type 'string' must have a '[Symbol.iterator]()' method that returns an iterator.
         log(x);
     }
 
     declare const aNumber: number;
 
     for (const x of aNumber) {
                     ~~~~~~~
-!!! error TS2488: Type 'number' must have a '[Symbol.iterator]()' method that returns an iterator.
+!!! error TS2495: Type 'number' is not an array type or a string type.
         log(x);
     }
 
     declare const anObject: { foo: string };
 
     for (const x of anObject) {
                     ~~~~~~~~
-!!! error TS2488: Type '{ foo: string; }' must have a '[Symbol.iterator]()' method that returns an iterator.
+!!! error TS2495: Type '{ foo: string; }' is not an array type or a string type.
         log(x);
     }

testdata/baselines/reference/submodule/compiler/arrayIterationLibES5TargetDifferent(nolib=false,target=es2015).types

@@ -6,7 +6,7 @@ declare function log(message?: any): void;
 >message : any
 
 for (const x of [1, 2, 3]) {
->x : any
+>x : number
 >[1, 2, 3] : number[]
 >1 : 1
 >2 : 2
@@ -15,20 +15,20 @@ for (const x of [1, 2, 3]) {
     log(x);
 >log(x) : void
 >log : (message?: any) => void
->x : any
+>x : number
 }
 
 declare const aString: string;
 >aString : string
 
 for (const x of aString) {
->x : any
+>x : string
 >aString : string
 
     log(x);
 >log(x) : void
 >log : (message?: any) => void
->x : any
+>x : string
 }
 
 declare const aNumber: number;

testdata/baselines/reference/submodule/compiler/arrayIterationLibES5TargetDifferent(nolib=false,target=esnext).errors.txt

@@ -1,38 +1,32 @@
-arrayIterationLibES5TargetDifferent.ts(3,17): error TS2488: Type 'number[]' must have a '[Symbol.iterator]()' method that returns an iterator.
-arrayIterationLibES5TargetDifferent.ts(9,17): error TS2488: Type 'string' must have a '[Symbol.iterator]()' method that returns an iterator.
-arrayIterationLibES5TargetDifferent.ts(15,17): error TS2488: Type 'number' must have a '[Symbol.iterator]()' method that returns an iterator.
-arrayIterationLibES5TargetDifferent.ts(21,17): error TS2488: Type '{ foo: string; }' must have a '[Symbol.iterator]()' method that returns an iterator.
+arrayIterationLibES5TargetDifferent.ts(15,17): error TS2495: Type 'number' is not an array type or a string type.
+arrayIterationLibES5TargetDifferent.ts(21,17): error TS2495: Type '{ foo: string; }' is not an array type or a string type.
 
 
-==== arrayIterationLibES5TargetDifferent.ts (4 errors) ====
+==== arrayIterationLibES5TargetDifferent.ts (2 errors) ====
     declare function log(message?: any): void;
 
     for (const x of [1, 2, 3]) {
-                    ~~~~~~~~~
-!!! error TS2488: Type 'number[]' must have a '[Symbol.iterator]()' method that returns an iterator.
         log(x);
     }
 
     declare const aString: string;
 
     for (const x of aString) {
-                    ~~~~~~~
-!!! error TS2488: Type 'string' must have a '[Symbol.iterator]()' method that returns an iterator.
         log(x);
     }
 
     declare const aNumber: number;
 
     for (const x of aNumber) {
                     ~~~~~~~
-!!! error TS2488: Type 'number' must have a '[Symbol.iterator]()' method that returns an iterator.
+!!! error TS2495: Type 'number' is not an array type or a string type.
         log(x);
     }
 
     declare const anObject: { foo: string };
 
     for (const x of anObject) {
                     ~~~~~~~~
-!!! error TS2488: Type '{ foo: string; }' must have a '[Symbol.iterator]()' method that returns an iterator.
+!!! error TS2495: Type '{ foo: string; }' is not an array type or a string type.
         log(x);
     }

testdata/baselines/reference/submodule/compiler/arrayIterationLibES5TargetDifferent(nolib=false,target=esnext).types

@@ -6,7 +6,7 @@ declare function log(message?: any): void;
 >message : any
 
 for (const x of [1, 2, 3]) {
->x : any
+>x : number
 >[1, 2, 3] : number[]
 >1 : 1
 >2 : 2
@@ -15,20 +15,20 @@ for (const x of [1, 2, 3]) {
     log(x);
 >log(x) : void
 >log : (message?: any) => void
->x : any
+>x : number
 }
 
 declare const aString: string;
 >aString : string
 
 for (const x of aString) {
->x : any
+>x : string
 >aString : string
 
     log(x);
 >log(x) : void
 >log : (message?: any) => void
->x : any
+>x : string
 }
 
 declare const aNumber: number;

testdata/baselines/reference/submodule/compiler/arrayIterationLibES5TargetDifferent(nolib=true,target=es2015).errors.txt

@@ -9,10 +9,6 @@ error TS2318: Cannot find global type 'Number'.
 error TS2318: Cannot find global type 'Object'.
 error TS2318: Cannot find global type 'RegExp'.
 error TS2318: Cannot find global type 'String'.
-arrayIterationLibES5TargetDifferent.ts(3,17): error TS2488: Type '{}' must have a '[Symbol.iterator]()' method that returns an iterator.
-arrayIterationLibES5TargetDifferent.ts(9,17): error TS2488: Type 'string' must have a '[Symbol.iterator]()' method that returns an iterator.
-arrayIterationLibES5TargetDifferent.ts(15,17): error TS2488: Type 'number' must have a '[Symbol.iterator]()' method that returns an iterator.
-arrayIterationLibES5TargetDifferent.ts(21,17): error TS2488: Type '{ foo: string; }' must have a '[Symbol.iterator]()' method that returns an iterator.
 
 
 !!! error TS5053: Option 'lib' cannot be specified with option 'noLib'.
@@ -26,35 +22,27 @@ arrayIterationLibES5TargetDifferent.ts(21,17): error TS2488: Type '{ foo: string
 !!! error TS2318: Cannot find global type 'Object'.
 !!! error TS2318: Cannot find global type 'RegExp'.
 !!! error TS2318: Cannot find global type 'String'.
-==== arrayIterationLibES5TargetDifferent.ts (4 errors) ====
+==== arrayIterationLibES5TargetDifferent.ts (0 errors) ====
     declare function log(message?: any): void;
 
     for (const x of [1, 2, 3]) {
-                    ~~~~~~~~~
-!!! error TS2488: Type '{}' must have a '[Symbol.iterator]()' method that returns an iterator.
         log(x);
     }
 
     declare const aString: string;
 
     for (const x of aString) {
-                    ~~~~~~~
-!!! error TS2488: Type 'string' must have a '[Symbol.iterator]()' method that returns an iterator.
         log(x);
     }
 
     declare const aNumber: number;
 
     for (const x of aNumber) {
-                    ~~~~~~~
-!!! error TS2488: Type 'number' must have a '[Symbol.iterator]()' method that returns an iterator.
         log(x);
     }
 
     declare const anObject: { foo: string };
 
     for (const x of anObject) {
-                    ~~~~~~~~
-!!! error TS2488: Type '{ foo: string; }' must have a '[Symbol.iterator]()' method that returns an iterator.
         log(x);
     }