Create type aliases for unresolved type symbols (#45976)

* Create type aliases for unresolved type symbols

* Accept new baselines

* Update fourslash tests

* Unresolved import aliases create tagged unresolved symbols

* Add comments

* Accept new baselines

* Add fourslash tests

Author: ahejlsberg

src/compiler/checker.ts

@@ -4957,6 +4957,7 @@ namespace ts {
         HasNeverType      = 1 << 17,        // Synthetic property with at least one never type in constituents
         Mapped            = 1 << 18,        // Property of mapped type
         StripOptional     = 1 << 19,        // Strip optionality in mapped property
+        Unresolved        = 1 << 20,        // Unresolved type alias symbol
         Synthetic = SyntheticProperty | SyntheticMethod,
         Discriminant = HasNonUniformType | HasLiteralType,
         Partial = ReadPartial | WritePartial

src/compiler/types.ts

@@ -2,5 +2,6 @@
 var v = (a: ) => {
 >v : Symbol(v, Decl(ArrowFunction1.ts, 0, 3))
 >a : Symbol(a, Decl(ArrowFunction1.ts, 0, 9))
+> : Symbol(unknown)
 
 };

tests/baselines/reference/ArrowFunction1.symbols

@@ -19,6 +19,7 @@ module clodule1 {
     function f(x: T) { }
 >f : Symbol(f, Decl(ClassAndModuleThatMergeWithModuleMemberThatUsesClassTypeParameter.ts, 8, 17))
 >x : Symbol(x, Decl(ClassAndModuleThatMergeWithModuleMemberThatUsesClassTypeParameter.ts, 9, 15))
+>T : Symbol(T)
 }
 
 class clodule2<T>{
@@ -38,10 +39,12 @@ module clodule2 {
 
     var x: T;
 >x : Symbol(x, Decl(ClassAndModuleThatMergeWithModuleMemberThatUsesClassTypeParameter.ts, 19, 7))
+>T : Symbol(T)
 
     class D<U extends T>{
 >D : Symbol(D, Decl(ClassAndModuleThatMergeWithModuleMemberThatUsesClassTypeParameter.ts, 19, 13))
 >U : Symbol(U, Decl(ClassAndModuleThatMergeWithModuleMemberThatUsesClassTypeParameter.ts, 21, 12))
+>T : Symbol(T)
 
         id: string;
 >id : Symbol(D.id, Decl(ClassAndModuleThatMergeWithModuleMemberThatUsesClassTypeParameter.ts, 21, 25))
@@ -92,6 +95,7 @@ module clodule4 {
 
         name: T;
 >name : Symbol(D.name, Decl(ClassAndModuleThatMergeWithModuleMemberThatUsesClassTypeParameter.ts, 44, 13))
+>T : Symbol(T)
     }
 }
 

tests/baselines/reference/ClassAndModuleThatMergeWithModuleMemberThatUsesClassTypeParameter.symbols

@@ -15,8 +15,8 @@ module clodule1 {
 >clodule1 : typeof clodule1
 
     function f(x: T) { }
->f : (x: any) => void
->x : any
+>f : (x: T) => void
+>x : T
 }
 
 class clodule2<T>{
@@ -33,7 +33,7 @@ module clodule2 {
 >clodule2 : typeof clodule2
 
     var x: T;
->x : any
+>x : T
 
     class D<U extends T>{
 >D : D<U>
@@ -83,7 +83,7 @@ module clodule4 {
 >D : D
 
         name: T;
->name : any
+>name : T
     }
 }
 

tests/baselines/reference/ClassAndModuleThatMergeWithModuleMemberThatUsesClassTypeParameter.types

@@ -5,5 +5,6 @@ function * foo() {
    // Legal to use 'yield' in a type context.
    var v: yield;
 >v : Symbol(v, Decl(FunctionDeclaration13_es6.ts, 2, 6))
+>yield : Symbol(yield)
 }
 

tests/baselines/reference/FunctionDeclaration13_es6.symbols

@@ -4,6 +4,6 @@ function * foo() {
 
    // Legal to use 'yield' in a type context.
    var v: yield;
->v : any
+>v : yield
 }
 

tests/baselines/reference/FunctionDeclaration13_es6.types

@@ -2,4 +2,5 @@
 function A(): (public B) => C {
 >A : Symbol(A, Decl(ParameterList5.ts, 0, 0))
 >B : Symbol(B, Decl(ParameterList5.ts, 0, 15))
+>C : Symbol(C)
 }

tests/baselines/reference/ParameterList5.symbols

@@ -1,5 +1,5 @@
 === tests/cases/compiler/ParameterList5.ts ===
 function A(): (public B) => C {
->A : () => (B: any) => any
+>A : () => (B: any) => C
 >B : any
 }

tests/baselines/reference/ParameterList5.types

@@ -1,4 +1,5 @@
 === tests/cases/conformance/parser/ecmascript5/TupleTypes/TupleType6.ts ===
 var v: [number,,]
 >v : Symbol(v, Decl(TupleType6.ts, 0, 3))
+> : Symbol(unknown)