Fix canHaveSyntheticDefault (#2101)

Author: jakebailey

internal/ast/ast.go

@@ -10757,7 +10757,9 @@ type SourceFile struct {
 	NodeCount                   int
 	TextCount                   int
 	CommonJSModuleIndicator     *Node
-	ExternalModuleIndicator     *Node
+	// If this is the SourceFile itself, then this module was "forced"
+	// to be an external module (previously "true").
+	ExternalModuleIndicator *Node
 
 	// Fields set by binder
 

internal/checker/checker.go

@@ -14440,7 +14440,7 @@ func (c *Checker) canHaveSyntheticDefault(file *ast.Node, moduleSymbol *ast.Symb
 	}
 
 	// JS files have a synthetic default if they do not contain ES2015+ module syntax (export = is not valid in js) _and_ do not have an __esModule marker
-	return !ast.IsExternalModule(file.AsSourceFile()) && c.resolveExportByName(moduleSymbol, "__esModule", nil /*sourceNode*/, dontResolveAlias) == nil
+	return (file.AsSourceFile().ExternalModuleIndicator == nil || file.AsSourceFile().ExternalModuleIndicator == file) && c.resolveExportByName(moduleSymbol, "__esModule", nil /*sourceNode*/, dontResolveAlias) == nil
 }
 
 func (c *Checker) getEmitSyntaxForModuleSpecifierExpression(usage *ast.Node) core.ResolutionMode {

testdata/baselines/reference/submodule/conformance/nodeModulesAllowJsCjsFromJs(module=node16).errors.txt

@@ -11,5 +11,7 @@ import foo from "./foo.cjs"
 >foo : Symbol(foo, Decl(bar.ts, 0, 6))
 
 foo.foo;
+>foo.foo : Symbol(foo.foo, Decl(foo.cjs, 0, 0))
 >foo : Symbol(foo, Decl(bar.ts, 0, 6))
+>foo : Symbol(foo.foo, Decl(foo.cjs, 0, 0))
 

testdata/baselines/reference/submodule/conformance/nodeModulesAllowJsCjsFromJs(module=node16).errors.txt.diff

@@ -8,11 +8,4 @@
 +>exports : Symbol("foo", Decl(foo.cjs, 0, 0))
  >foo : Symbol(foo, Decl(foo.cjs, 0, 0))
 
- === bar.ts ===
-@@= skipped -8, +8 lines =@@
- >foo : Symbol(foo, Decl(bar.ts, 0, 6))
-
- foo.foo;
-->foo.foo : Symbol(foo.foo, Decl(foo.cjs, 0, 0))
- >foo : Symbol(foo, Decl(bar.ts, 0, 6))
-->foo : Symbol(foo.foo, Decl(foo.cjs, 0, 0))
+ === bar.ts ===

testdata/baselines/reference/submodule/conformance/nodeModulesAllowJsCjsFromJs(module=node16).symbols

@@ -10,10 +10,10 @@ exports.foo = "foo"
 
 === bar.ts ===
 import foo from "./foo.cjs"
->foo : any
+>foo : typeof foo
 
 foo.foo;
->foo.foo : any
->foo : any
->foo : any
+>foo.foo : "foo"
+>foo : typeof foo
+>foo : "foo"