Revert microsoft#26762, microsoft#26726, and microsoft#26317 in prepa…

…ration for a clean PR fixing all the issues.

src/compiler/checker.ts

@@ -1211,23 +1211,17 @@ namespace ts {
                                     // local types not visible outside the function body
                                     : false;
                             }
-                            if (meaning & SymbolFlags.Value && result.flags & SymbolFlags.Variable) {
-                                // expression inside parameter will lookup as normal variable scope when targeting es2015+
-                                if (compilerOptions.target && compilerOptions.target >= ScriptTarget.ES2015 && isParameter(lastLocation) && !isParameterPropertyDeclaration(lastLocation) && result.valueDeclaration.pos > lastLocation.end) {
-                                    useResult = false;
-                                }
-                                else if (result.flags & SymbolFlags.FunctionScopedVariable) {
-                                    // parameters are visible only inside function body, parameter list and return type
-                                    // technically for parameter list case here we might mix parameters and variables declared in function,
-                                    // however it is detected separately when checking initializers of parameters
-                                    // to make sure that they reference no variables declared after them.
-                                    useResult =
+                            if (meaning & SymbolFlags.Value && result.flags & SymbolFlags.FunctionScopedVariable) {
+                                // parameters are visible only inside function body, parameter list and return type
+                                // technically for parameter list case here we might mix parameters and variables declared in function,
+                                // however it is detected separately when checking initializers of parameters
+                                // to make sure that they reference no variables declared after them.
+                                useResult =
                                     lastLocation.kind === SyntaxKind.Parameter ||
                                     (
                                         lastLocation === (<FunctionLikeDeclaration>location).type &&
                                         !!findAncestor(result.valueDeclaration, isParameter)
                                     );
-                                }
                             }
                         }
                         else if (location.kind === SyntaxKind.ConditionalType) {

tests/baselines/reference/genericRestParameters1.errors.txt

@@ -1,7 +1,11 @@
 tests/cases/conformance/types/rest/genericRestParameters1.ts(22,1): error TS2556: Expected 3 arguments, but got 1 or more.
 tests/cases/conformance/types/rest/genericRestParameters1.ts(31,1): error TS2556: Expected 3 arguments, but got 1 or more.
 tests/cases/conformance/types/rest/genericRestParameters1.ts(133,40): error TS2344: Type '(...args: T) => void' does not satisfy the constraint '(...args: any[]) => any'.
+  Types of parameters 'args' and 'args' are incompatible.
+    Type 'any[]' is not assignable to type 'T'.
 tests/cases/conformance/types/rest/genericRestParameters1.ts(134,51): error TS2344: Type 'new (...args: T) => void' does not satisfy the constraint 'new (...args: any[]) => any'.
+  Types of parameters 'args' and 'args' are incompatible.
+    Type 'any[]' is not assignable to type 'T'.
 tests/cases/conformance/types/rest/genericRestParameters1.ts(135,23): error TS2344: Type 'Function' does not satisfy the constraint '(...args: any[]) => any'.
   Type 'Function' provides no match for the signature '(...args: any[]): any'.
 tests/cases/conformance/types/rest/genericRestParameters1.ts(164,1): error TS2322: Type '(a: never) => void' is not assignable to type '(...args: any[]) => void'.
@@ -149,9 +153,13 @@ tests/cases/conformance/types/rest/genericRestParameters1.ts(164,1): error TS232
     type T07<T extends any[]> = Parameters<(...args: T) => void>;
                                            ~~~~~~~~~~~~~~~~~~~~
 !!! error TS2344: Type '(...args: T) => void' does not satisfy the constraint '(...args: any[]) => any'.
+!!! error TS2344:   Types of parameters 'args' and 'args' are incompatible.
+!!! error TS2344:     Type 'any[]' is not assignable to type 'T'.
     type T08<T extends any[]> = ConstructorParameters<new (...args: T) => void>;
                                                       ~~~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS2344: Type 'new (...args: T) => void' does not satisfy the constraint 'new (...args: any[]) => any'.
+!!! error TS2344:   Types of parameters 'args' and 'args' are incompatible.
+!!! error TS2344:     Type 'any[]' is not assignable to type 'T'.
     type T09 = Parameters<Function>;
                           ~~~~~~~~
 !!! error TS2344: Type 'Function' does not satisfy the constraint '(...args: any[]) => any'.

tests/baselines/reference/genericRestParameters2.errors.txt

@@ -1,4 +1,7 @@
 tests/cases/conformance/types/rest/genericRestParameters2.ts(71,40): error TS2344: Type '(x: string, ...args: T) => void' does not satisfy the constraint '(...args: any[]) => any'.
+  Types of parameters 'x' and 'args' are incompatible.
+    Type 'any[]' is not assignable to type '[string, ...any[]]'.
+      Property '0' is missing in type 'any[]'.
 
 
 ==== tests/cases/conformance/types/rest/genericRestParameters2.ts (1 errors) ====
@@ -75,6 +78,9 @@ tests/cases/conformance/types/rest/genericRestParameters2.ts(71,40): error TS234
     type T05<T extends any[]> = Parameters<(x: string, ...args: T) => void>;
                                            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS2344: Type '(x: string, ...args: T) => void' does not satisfy the constraint '(...args: any[]) => any'.
+!!! error TS2344:   Types of parameters 'x' and 'args' are incompatible.
+!!! error TS2344:     Type 'any[]' is not assignable to type '[string, ...any[]]'.
+!!! error TS2344:       Property '0' is missing in type 'any[]'.
     type T06 = T05<[number, ...boolean[]]>;
 
     type P1<T extends Function> = T extends (head: infer A, ...tail: infer B) => any ? { head: A, tail: B } : any[];

tests/baselines/reference/parameterInitializersForwardReferencing1_es6.errors.txt

@@ -1,21 +1,31 @@
+tests/cases/conformance/functions/parameterInitializersForwardReferencing1_es6.ts(3,20): error TS2373: Initializer of parameter 'bar' cannot reference identifier 'foo' declared after it.
+tests/cases/conformance/functions/parameterInitializersForwardReferencing1_es6.ts(8,27): error TS2373: Initializer of parameter 'bar' cannot reference identifier 'foo' declared after it.
+tests/cases/conformance/functions/parameterInitializersForwardReferencing1_es6.ts(13,20): error TS2373: Initializer of parameter 'bar' cannot reference identifier 'foo' declared after it.
 tests/cases/conformance/functions/parameterInitializersForwardReferencing1_es6.ts(21,18): error TS2372: Parameter 'a' cannot be referenced in its initializer.
 tests/cases/conformance/functions/parameterInitializersForwardReferencing1_es6.ts(25,22): error TS2372: Parameter 'async' cannot be referenced in its initializer.
+tests/cases/conformance/functions/parameterInitializersForwardReferencing1_es6.ts(29,15): error TS2448: Block-scoped variable 'foo' used before its declaration.
 
 
-==== tests/cases/conformance/functions/parameterInitializersForwardReferencing1_es6.ts (2 errors) ====
+==== tests/cases/conformance/functions/parameterInitializersForwardReferencing1_es6.ts (6 errors) ====
     let foo: string = "";
 
     function f1 (bar = foo) { // unexpected compiler error; works at runtime
+                       ~~~
+!!! error TS2373: Initializer of parameter 'bar' cannot reference identifier 'foo' declared after it.
         var foo: number = 2;
         return bar; // returns 1
     }
 
     function f2 (bar = (baz = foo) => baz) { // unexpected compiler error; works at runtime
+                              ~~~
+!!! error TS2373: Initializer of parameter 'bar' cannot reference identifier 'foo' declared after it.
         var foo: number = 2;
         return bar(); // returns 1
     }
 
     function f3 (bar = foo, foo = 2) { // correct compiler error, error at runtime
+                       ~~~
+!!! error TS2373: Initializer of parameter 'bar' cannot reference identifier 'foo' declared after it.
         return bar;
     }
 
@@ -36,6 +46,9 @@ tests/cases/conformance/functions/parameterInitializersForwardReferencing1_es6.t
     }
 
     function f7({[foo]: bar}: any[]) {
+                  ~~~
+!!! error TS2448: Block-scoped variable 'foo' used before its declaration.
+!!! related TS2728 tests/cases/conformance/functions/parameterInitializersForwardReferencing1_es6.ts:30:9: 'foo' is declared here.
         let foo: number = 2;
     }
 

tests/baselines/reference/parameterInitializersForwardReferencing1_es6.symbols

@@ -5,7 +5,7 @@ let foo: string = "";
 function f1 (bar = foo) { // unexpected compiler error; works at runtime
 >f1 : Symbol(f1, Decl(parameterInitializersForwardReferencing1_es6.ts, 0, 21))
 >bar : Symbol(bar, Decl(parameterInitializersForwardReferencing1_es6.ts, 2, 13))
->foo : Symbol(foo, Decl(parameterInitializersForwardReferencing1_es6.ts, 0, 3))
+>foo : Symbol(foo, Decl(parameterInitializersForwardReferencing1_es6.ts, 3, 7))
 
     var foo: number = 2;
 >foo : Symbol(foo, Decl(parameterInitializersForwardReferencing1_es6.ts, 3, 7))
@@ -18,7 +18,7 @@ function f2 (bar = (baz = foo) => baz) { // unexpected compiler error; works at
 >f2 : Symbol(f2, Decl(parameterInitializersForwardReferencing1_es6.ts, 5, 1))
 >bar : Symbol(bar, Decl(parameterInitializersForwardReferencing1_es6.ts, 7, 13))
 >baz : Symbol(baz, Decl(parameterInitializersForwardReferencing1_es6.ts, 7, 20))
->foo : Symbol(foo, Decl(parameterInitializersForwardReferencing1_es6.ts, 0, 3))
+>foo : Symbol(foo, Decl(parameterInitializersForwardReferencing1_es6.ts, 8, 7))
 >baz : Symbol(baz, Decl(parameterInitializersForwardReferencing1_es6.ts, 7, 20))
 
     var foo: number = 2;
@@ -31,7 +31,7 @@ function f2 (bar = (baz = foo) => baz) { // unexpected compiler error; works at
 function f3 (bar = foo, foo = 2) { // correct compiler error, error at runtime
 >f3 : Symbol(f3, Decl(parameterInitializersForwardReferencing1_es6.ts, 10, 1))
 >bar : Symbol(bar, Decl(parameterInitializersForwardReferencing1_es6.ts, 12, 13))
->foo : Symbol(foo, Decl(parameterInitializersForwardReferencing1_es6.ts, 0, 3))
+>foo : Symbol(foo, Decl(parameterInitializersForwardReferencing1_es6.ts, 12, 23))
 >foo : Symbol(foo, Decl(parameterInitializersForwardReferencing1_es6.ts, 12, 23))
 
     return bar;
@@ -68,7 +68,7 @@ function f6 (async = async) {
 
 function f7({[foo]: bar}: any[]) {
 >f7 : Symbol(f7, Decl(parameterInitializersForwardReferencing1_es6.ts, 26, 1))
->foo : Symbol(foo, Decl(parameterInitializersForwardReferencing1_es6.ts, 0, 3))
+>foo : Symbol(foo, Decl(parameterInitializersForwardReferencing1_es6.ts, 29, 7))
 >bar : Symbol(bar, Decl(parameterInitializersForwardReferencing1_es6.ts, 28, 13))
 
     let foo: number = 2;

tests/baselines/reference/parameterInitializersForwardReferencing1_es6.types

@@ -4,44 +4,44 @@ let foo: string = "";
 >"" : ""
 
 function f1 (bar = foo) { // unexpected compiler error; works at runtime
->f1 : (bar?: string) => string
->bar : string
->foo : string
+>f1 : (bar?: number) => number
+>bar : number
+>foo : number
 
     var foo: number = 2;
 >foo : number
 >2 : 2
 
     return bar; // returns 1
->bar : string
+>bar : number
 }
 
 function f2 (bar = (baz = foo) => baz) { // unexpected compiler error; works at runtime
->f2 : (bar?: (baz?: string) => string) => string
->bar : (baz?: string) => string
->(baz = foo) => baz : (baz?: string) => string
->baz : string
->foo : string
->baz : string
+>f2 : (bar?: (baz?: number) => number) => number
+>bar : (baz?: number) => number
+>(baz = foo) => baz : (baz?: number) => number
+>baz : number
+>foo : number
+>baz : number
 
     var foo: number = 2;
 >foo : number
 >2 : 2
 
     return bar(); // returns 1
->bar() : string
->bar : (baz?: string) => string
+>bar() : number
+>bar : (baz?: number) => number
 }
 
 function f3 (bar = foo, foo = 2) { // correct compiler error, error at runtime
->f3 : (bar?: string, foo?: number) => string
->bar : string
->foo : string
+>f3 : (bar?: number, foo?: number) => number
+>bar : number
+>foo : number
 >foo : number
 >2 : 2
 
     return bar;
->bar : string
+>bar : number
 }
 
 function f4 (foo, bar = foo) {
@@ -74,7 +74,7 @@ function f6 (async = async) {
 
 function f7({[foo]: bar}: any[]) {
 >f7 : ({ [foo]: bar }: any[]) => void
->foo : string
+>foo : number
 >bar : any
 
     let foo: number = 2;