Improve error position/range for arrow functions with expression body

src/compiler/checker.ts

@@ -45798,7 +45798,10 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             : exprType;
 
         const effectiveExpr = expr && getEffectiveCheckNode(expr); // The effective expression for diagnostics purposes.
-        const errorNode = inReturnStatement && !inConditionalExpression ? node : effectiveExpr;
+        const errorNode = inConditionalExpression ? effectiveExpr :
+            inReturnStatement ? node :
+            isArrowFunction(node.parent) && node.parent.type !== undefined ? node.parent.type :
+            effectiveExpr;
 
         // If the return type is not narrowable, we simply check if the return expression type is assignable to the return type.
         if (!(unwrappedReturnType.flags & (TypeFlags.IndexedAccess | TypeFlags.Conditional)) || !couldContainTypeVariables(unwrappedReturnType)) {

tests/baselines/reference/arrowFunctionErrorSpan.errors.txt

@@ -19,9 +19,11 @@ arrowFunctionErrorSpan.ts(43,5): error TS2345: Argument of type '() => void' is
   Type 'void' is not assignable to type 'number'.
 arrowFunctionErrorSpan.ts(52,3): error TS2345: Argument of type '(_: any) => number' is not assignable to parameter of type '() => number'.
   Target signature provides too few arguments. Expected 1 or more, but got 0.
+arrowFunctionErrorSpan.ts(55,7): error TS2355: A function whose declared type is neither 'undefined', 'void', nor 'any' must return a value.
+arrowFunctionErrorSpan.ts(57,7): error TS2322: Type 'string' is not assignable to type 'number'.
 
 
-==== arrowFunctionErrorSpan.ts (11 errors) ====
+==== arrowFunctionErrorSpan.ts (13 errors) ====
     function f(a: () => number) { }
 
     // oneliner
@@ -112,4 +114,12 @@ arrowFunctionErrorSpan.ts(52,3): error TS2345: Argument of type '(_: any) => num
     ~~~~~
 !!! error TS2345: Argument of type '(_: any) => number' is not assignable to parameter of type '() => number'.
 !!! error TS2345:   Target signature provides too few arguments. Expected 1 or more, but got 0.
+
+    f((): number => { });
+          ~~~~~~
+!!! error TS2355: A function whose declared type is neither 'undefined', 'void', nor 'any' must return a value.
+
+    f((): number => '');
+          ~~~~~~
+!!! error TS2322: Type 'string' is not assignable to type 'number'.
 

tests/baselines/reference/arrowFunctionErrorSpan.js

@@ -54,6 +54,10 @@ f(  // comment 1
 // body is not a block
 f(_ => 1 +
     2);
+
+f((): number => { });
+
+f((): number => '');
 
 
 //// [arrowFunctionErrorSpan.js]
@@ -91,3 +95,5 @@ function () {
 // body is not a block
 f(function (_) { return 1 +
     2; });
+f(function () { });
+f(function () { return ''; });

tests/baselines/reference/arrowFunctionErrorSpan.symbols

@@ -81,3 +81,9 @@ f(_ => 1 +
 
     2);
 
+f((): number => { });
+>f : Symbol(f, Decl(arrowFunctionErrorSpan.ts, 0, 0))
+
+f((): number => '');
+>f : Symbol(f, Decl(arrowFunctionErrorSpan.ts, 0, 0))
+

tests/baselines/reference/arrowFunctionErrorSpan.types

@@ -145,3 +145,21 @@ f(_ => 1 +
 >2 : 2
 >  : ^
 
+f((): number => { });
+>f((): number => { }) : void
+>                     : ^^^^
+>f : (a: () => number) => void
+>  : ^ ^^            ^^^^^^^^^
+>(): number => { } : () => number
+>                  : ^^^^^^      
+
+f((): number => '');
+>f((): number => '') : void
+>                    : ^^^^
+>f : (a: () => number) => void
+>  : ^ ^^            ^^^^^^^^^
+>(): number => '' : () => number
+>                 : ^^^^^^      
+>'' : ""
+>   : ^^
+

tests/baselines/reference/arrowFunctionReturnTypeErrorSpan.errors.txt

@@ -0,0 +1,41 @@
+arrowFunctionReturnTypeErrorSpan.ts(2,7): error TS2451: Cannot redeclare block-scoped variable 'a'.
+arrowFunctionReturnTypeErrorSpan.ts(3,3): error TS2322: Type 'string' is not assignable to type 'number'.
+arrowFunctionReturnTypeErrorSpan.ts(6,7): error TS2451: Cannot redeclare block-scoped variable 'a'.
+arrowFunctionReturnTypeErrorSpan.ts(7,10): error TS2304: Cannot find name 'missing'.
+arrowFunctionReturnTypeErrorSpan.ts(11,15): error TS2322: Type 'string' is not assignable to type 'number'.
+arrowFunctionReturnTypeErrorSpan.ts(14,15): error TS2322: Type 'string' is not assignable to type 'number'.
+arrowFunctionReturnTypeErrorSpan.ts(16,25): error TS2304: Cannot find name 'missing'.
+
+
+==== arrowFunctionReturnTypeErrorSpan.ts (7 errors) ====
+    // block body
+    const a = (): number => {
+          ~
+!!! error TS2451: Cannot redeclare block-scoped variable 'a'.
+      return "foo";
+      ~~~~~~
+!!! error TS2322: Type 'string' is not assignable to type 'number'.
+    };
+
+    const a = (): number => {
+          ~
+!!! error TS2451: Cannot redeclare block-scoped variable 'a'.
+      return missing;
+             ~~~~~~~
+!!! error TS2304: Cannot find name 'missing'.
+    };
+
+    // expression body
+    const b = (): number => "foo";
+                  ~~~~~~
+!!! error TS2322: Type 'string' is not assignable to type 'number'.
+
+    type F<T> = T;
+    const c = (): F<number> => "foo";
+                  ~~~~~~~~~
+!!! error TS2322: Type 'string' is not assignable to type 'number'.
+
+    const d = (): number => missing;
+                            ~~~~~~~
+!!! error TS2304: Cannot find name 'missing'.
+

tests/baselines/reference/arrowFunctionReturnTypeErrorSpan.js

@@ -0,0 +1,33 @@
+//// [tests/cases/compiler/arrowFunctionReturnTypeErrorSpan.ts] ////
+
+//// [arrowFunctionReturnTypeErrorSpan.ts]
+// block body
+const a = (): number => {
+  return "foo";
+};
+
+const a = (): number => {
+  return missing;
+};
+
+// expression body
+const b = (): number => "foo";
+
+type F<T> = T;
+const c = (): F<number> => "foo";
+
+const d = (): number => missing;
+
+
+//// [arrowFunctionReturnTypeErrorSpan.js]
+// block body
+var a = function () {
+    return "foo";
+};
+var a = function () {
+    return missing;
+};
+// expression body
+var b = function () { return "foo"; };
+var c = function () { return "foo"; };
+var d = function () { return missing; };

tests/baselines/reference/arrowFunctionReturnTypeErrorSpan.symbols

@@ -0,0 +1,32 @@
+//// [tests/cases/compiler/arrowFunctionReturnTypeErrorSpan.ts] ////
+
+=== arrowFunctionReturnTypeErrorSpan.ts ===
+// block body
+const a = (): number => {
+>a : Symbol(a, Decl(arrowFunctionReturnTypeErrorSpan.ts, 1, 5))
+
+  return "foo";
+};
+
+const a = (): number => {
+>a : Symbol(a, Decl(arrowFunctionReturnTypeErrorSpan.ts, 5, 5))
+
+  return missing;
+};
+
+// expression body
+const b = (): number => "foo";
+>b : Symbol(b, Decl(arrowFunctionReturnTypeErrorSpan.ts, 10, 5))
+
+type F<T> = T;
+>F : Symbol(F, Decl(arrowFunctionReturnTypeErrorSpan.ts, 10, 30))
+>T : Symbol(T, Decl(arrowFunctionReturnTypeErrorSpan.ts, 12, 7))
+>T : Symbol(T, Decl(arrowFunctionReturnTypeErrorSpan.ts, 12, 7))
+
+const c = (): F<number> => "foo";
+>c : Symbol(c, Decl(arrowFunctionReturnTypeErrorSpan.ts, 13, 5))
+>F : Symbol(F, Decl(arrowFunctionReturnTypeErrorSpan.ts, 10, 30))
+
+const d = (): number => missing;
+>d : Symbol(d, Decl(arrowFunctionReturnTypeErrorSpan.ts, 15, 5))
+

tests/baselines/reference/arrowFunctionReturnTypeErrorSpan.types

@@ -0,0 +1,57 @@
+//// [tests/cases/compiler/arrowFunctionReturnTypeErrorSpan.ts] ////
+
+=== arrowFunctionReturnTypeErrorSpan.ts ===
+// block body
+const a = (): number => {
+>a : () => number
+>  : ^^^^^^      
+>(): number => {  return "foo";} : () => number
+>                                : ^^^^^^      
+
+  return "foo";
+>"foo" : "foo"
+>      : ^^^^^
+
+};
+
+const a = (): number => {
+>a : () => number
+>  : ^^^^^^      
+>(): number => {  return missing;} : () => number
+>                                  : ^^^^^^      
+
+  return missing;
+>missing : any
+>        : ^^^
+
+};
+
+// expression body
+const b = (): number => "foo";
+>b : () => number
+>  : ^^^^^^      
+>(): number => "foo" : () => number
+>                    : ^^^^^^      
+>"foo" : "foo"
+>      : ^^^^^
+
+type F<T> = T;
+>F : T
+>  : ^
+
+const c = (): F<number> => "foo";
+>c : () => F<number>
+>  : ^^^^^^         
+>(): F<number> => "foo" : () => F<number>
+>                       : ^^^^^^         
+>"foo" : "foo"
+>      : ^^^^^
+
+const d = (): number => missing;
+>d : () => number
+>  : ^^^^^^      
+>(): number => missing : () => number
+>                      : ^^^^^^      
+>missing : any
+>        : ^^^
+

tests/baselines/reference/conditionalTypes1.errors.txt

@@ -73,7 +73,7 @@ conditionalTypes1.ts(160,5): error TS2322: Type 'T' is not assignable to type 'Z
   Type 'string | number' is not assignable to type 'ZeroOf<T>'.
     Type 'string' is not assignable to type 'ZeroOf<T>'.
 conditionalTypes1.ts(263,9): error TS2403: Subsequent variable declarations must have the same type.  Variable 'z' must be of type 'T1', but here has type 'Foo<T & U>'.
-conditionalTypes1.ts(288,43): error TS2322: Type 'T95<U>' is not assignable to type 'T94<U>'.
+conditionalTypes1.ts(288,33): error TS2322: Type 'T95<U>' is not assignable to type 'T94<U>'.
   Type 'number | boolean' is not assignable to type 'T94<U>'.
     Type 'number' is not assignable to type 'T94<U>'.
       Type 'boolean' is not assignable to type 'true'.
@@ -465,7 +465,7 @@ conditionalTypes1.ts(288,43): error TS2322: Type 'T95<U>' is not assignable to t
     type T95<T> = T extends string ? boolean : number;
     const f44 = <U>(value: T94<U>): T95<U> => value;
     const f45 = <U>(value: T95<U>): T94<U> => value;  // Error
-                                              ~~~~~
+                                    ~~~~~~
 !!! error TS2322: Type 'T95<U>' is not assignable to type 'T94<U>'.
 !!! error TS2322:   Type 'number | boolean' is not assignable to type 'T94<U>'.
 !!! error TS2322:     Type 'number' is not assignable to type 'T94<U>'.

tests/baselines/reference/mappedTypeConstraints2.errors.txt

@@ -6,7 +6,7 @@ mappedTypeConstraints2.ts(16,11): error TS2322: Type 'Mapped3<K>[Uppercase<K>]'
 mappedTypeConstraints2.ts(42,7): error TS2322: Type 'Mapped6<K>[keyof Mapped6<K>]' is not assignable to type '`_${string}`'.
   Type 'Mapped6<K>[string] | Mapped6<K>[number] | Mapped6<K>[symbol]' is not assignable to type '`_${string}`'.
     Type 'Mapped6<K>[string]' is not assignable to type '`_${string}`'.
-mappedTypeConstraints2.ts(51,57): error TS2322: Type 'Foo<T>[`get${T}`]' is not assignable to type 'T'.
+mappedTypeConstraints2.ts(51,52): error TS2322: Type 'Foo<T>[`get${T}`]' is not assignable to type 'T'.
   'T' could be instantiated with an arbitrary type which could be unrelated to 'Foo<T>[`get${T}`]'.
 mappedTypeConstraints2.ts(82,9): error TS2322: Type 'ObjectWithUnderscoredKeys<K>[`_${K}`]' is not assignable to type 'true'.
   Type 'ObjectWithUnderscoredKeys<K>[`_${string}`]' is not assignable to type 'true'.
@@ -75,7 +75,7 @@ mappedTypeConstraints2.ts(82,9): error TS2322: Type 'ObjectWithUnderscoredKeys<K
     };
 
     const get = <T extends string>(t: T, foo: Foo<T>): T => foo[`get${t}`];  // Type 'Foo<T>[`get${T}`]' is not assignable to type 'T'
-                                                            ~~~~~~~~~~~~~~
+                                                       ~
 !!! error TS2322: Type 'Foo<T>[`get${T}`]' is not assignable to type 'T'.
 !!! error TS2322:   'T' could be instantiated with an arbitrary type which could be unrelated to 'Foo<T>[`get${T}`]'.
 

tests/baselines/reference/typeSatisfaction_errorLocations1.errors.txt

@@ -26,13 +26,13 @@ typeSatisfaction_errorLocations1.ts(36,9): error TS2345: Argument of type 'strin
 typeSatisfaction_errorLocations1.ts(39,3): error TS2322: Type 'string' is not assignable to type 'number'.
 typeSatisfaction_errorLocations1.ts(43,3): error TS2322: Type 'string' is not assignable to type 'number'.
 typeSatisfaction_errorLocations1.ts(43,16): error TS1360: Type 'string' does not satisfy the expected type 'number'.
-typeSatisfaction_errorLocations1.ts(46,22): error TS2741: Property 'a' is missing in type '{}' but required in type '{ a: true; }'.
+typeSatisfaction_errorLocations1.ts(46,6): error TS2741: Property 'a' is missing in type '{}' but required in type '{ a: true; }'.
 typeSatisfaction_errorLocations1.ts(47,24): error TS2322: Type 'number' is not assignable to type 'true'.
-typeSatisfaction_errorLocations1.ts(48,21): error TS2322: Type '{ a: number; }' is not assignable to type '{ a: true; }'.
+typeSatisfaction_errorLocations1.ts(48,6): error TS2322: Type '{ a: number; }' is not assignable to type '{ a: true; }'.
   Types of property 'a' are incompatible.
     Type 'number' is not assignable to type 'true'.
-typeSatisfaction_errorLocations1.ts(50,23): error TS2741: Property 'a' is missing in type '{}' but required in type '{ a: true; }'.
-typeSatisfaction_errorLocations1.ts(51,24): error TS2741: Property 'a' is missing in type '{}' but required in type '{ a: true; }'.
+typeSatisfaction_errorLocations1.ts(50,6): error TS2741: Property 'a' is missing in type '{}' but required in type '{ a: true; }'.
+typeSatisfaction_errorLocations1.ts(51,6): error TS2741: Property 'a' is missing in type '{}' but required in type '{ a: true; }'.
 
 
 ==== typeSatisfaction_errorLocations1.ts (24 errors) ====
@@ -133,25 +133,25 @@ typeSatisfaction_errorLocations1.ts(51,24): error TS2741: Property 'a' is missin
     }
 
     ((): { a: true } => ({}) satisfies unknown)();
-                         ~~
+         ~~~~~~~~~~~
 !!! error TS2741: Property 'a' is missing in type '{}' but required in type '{ a: true; }'.
 !!! related TS2728 typeSatisfaction_errorLocations1.ts:46:8: 'a' is declared here.
     ((): { a: true } => ({ a: 1 }) satisfies unknown)();
                            ~
 !!! error TS2322: Type 'number' is not assignable to type 'true'.
 !!! related TS6500 typeSatisfaction_errorLocations1.ts:47:8: The expected type comes from property 'a' which is declared here on type '{ a: true; }'
     ((): { a: true } => obj1 satisfies unknown)();
-                        ~~~~
+         ~~~~~~~~~~~
 !!! error TS2322: Type '{ a: number; }' is not assignable to type '{ a: true; }'.
 !!! error TS2322:   Types of property 'a' are incompatible.
 !!! error TS2322:     Type 'number' is not assignable to type 'true'.
 
     ((): { a: true } => (({}) satisfies unknown) satisfies unknown)();
-                          ~~
+         ~~~~~~~~~~~
 !!! error TS2741: Property 'a' is missing in type '{}' but required in type '{ a: true; }'.
 !!! related TS2728 typeSatisfaction_errorLocations1.ts:50:8: 'a' is declared here.
     ((): { a: true } => ((({}) satisfies unknown)) satisfies unknown)();
-                           ~~
+         ~~~~~~~~~~~
 !!! error TS2741: Property 'a' is missing in type '{}' but required in type '{ a: true; }'.
 !!! related TS2728 typeSatisfaction_errorLocations1.ts:51:8: 'a' is declared here.
 

tests/cases/compiler/arrowFunctionErrorSpan.ts

@@ -51,3 +51,7 @@ f(  // comment 1
 // body is not a block
 f(_ => 1 +
     2);
+
+f((): number => { });
+
+f((): number => '');

tests/cases/compiler/arrowFunctionReturnTypeErrorSpan.ts

@@ -0,0 +1,16 @@
+// block body
+const a = (): number => {
+  return "foo";
+};
+
+const a = (): number => {
+  return missing;
+};
+
+// expression body
+const b = (): number => "foo";
+
+type F<T> = T;
+const c = (): F<number> => "foo";
+
+const d = (): number => missing;