Improve error message when comparing non-comparable types

src/compiler/checker.ts

@@ -22834,10 +22834,9 @@ namespace ts {
                 switch (operatorToken.kind) {
                     case SyntaxKind.EqualsEqualsEqualsToken:
                     case SyntaxKind.EqualsEqualsToken:
-                        return error(errNode, Diagnostics.This_condition_will_always_return_0_since_the_types_1_and_2_have_no_overlap, "false", leftStr, rightStr);
                     case SyntaxKind.ExclamationEqualsEqualsToken:
                     case SyntaxKind.ExclamationEqualsToken:
-                        return error(errNode, Diagnostics.This_condition_will_always_return_0_since_the_types_1_and_2_have_no_overlap, "true", leftStr, rightStr);
+                        return error(errNode, Diagnostics.Comparison_of_expressions_of_types_0_and_1_may_be_a_mistake_because_neither_type_sufficiently_overlaps_with_the_other_If_this_was_intentional_convert_one_of_the_expressions_to_unknown_first, leftStr, rightStr);
                     }
                 return undefined;
             }

src/compiler/diagnosticMessages.json

@@ -1292,7 +1292,7 @@
         "category": "Error",
         "code": 2366
     },
-    "This condition will always return '{0}' since the types '{1}' and '{2}' have no overlap.": {
+    "Comparison of expressions of types '{0}' and '{1}' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.": {
         "category": "Error",
         "code": 2367
     },

src/testRunner/unittests/tsserver/skipLibCheck.ts

@@ -167,7 +167,7 @@ namespace ts.projectSystem {
             );
             const errorResult = <protocol.Diagnostic[]>session.executeCommand(getErrRequest).response;
             assert.isTrue(errorResult.length === 1);
-            assert.equal(errorResult[0].code, Diagnostics.This_condition_will_always_return_0_since_the_types_1_and_2_have_no_overlap.code);
+            assert.equal(errorResult[0].code, Diagnostics.Comparison_of_expressions_of_types_0_and_1_may_be_a_mistake_because_neither_type_sufficiently_overlaps_with_the_other_If_this_was_intentional_convert_one_of_the_expressions_to_unknown_first.code);
         });
 
         it("should report semantic errors for configured js project with '// @ts-check' and skipLibCheck=true", () => {
@@ -194,7 +194,7 @@ namespace ts.projectSystem {
             );
             const errorResult = <protocol.Diagnostic[]>session.executeCommand(getErrRequest).response;
             assert.isTrue(errorResult.length === 1);
-            assert.equal(errorResult[0].code, Diagnostics.This_condition_will_always_return_0_since_the_types_1_and_2_have_no_overlap.code);
+            assert.equal(errorResult[0].code, Diagnostics.Comparison_of_expressions_of_types_0_and_1_may_be_a_mistake_because_neither_type_sufficiently_overlaps_with_the_other_If_this_was_intentional_convert_one_of_the_expressions_to_unknown_first.code);
         });
 
         it("should report semantic errors for configured js project with checkJs=true and skipLibCheck=true", () => {
@@ -223,7 +223,7 @@ namespace ts.projectSystem {
             );
             const errorResult = <protocol.Diagnostic[]>session.executeCommand(getErrRequest).response;
             assert.isTrue(errorResult.length === 1);
-            assert.equal(errorResult[0].code, Diagnostics.This_condition_will_always_return_0_since_the_types_1_and_2_have_no_overlap.code);
+            assert.equal(errorResult[0].code, Diagnostics.Comparison_of_expressions_of_types_0_and_1_may_be_a_mistake_because_neither_type_sufficiently_overlaps_with_the_other_If_this_was_intentional_convert_one_of_the_expressions_to_unknown_first.code);
         });
     });
 }

tests/baselines/reference/capturedLetConstInLoop5.errors.txt

@@ -1,5 +1,5 @@
-tests/cases/compiler/capturedLetConstInLoop5.ts(174,13): error TS2367: This condition will always return 'false' since the types '0' and '1' have no overlap.
-tests/cases/compiler/capturedLetConstInLoop5.ts(229,13): error TS2367: This condition will always return 'false' since the types '0' and '1' have no overlap.
+tests/cases/compiler/capturedLetConstInLoop5.ts(174,13): error TS2367: Comparison of expressions of types '0' and '1' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.
+tests/cases/compiler/capturedLetConstInLoop5.ts(229,13): error TS2367: Comparison of expressions of types '0' and '1' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.
 
 
 ==== tests/cases/compiler/capturedLetConstInLoop5.ts (2 errors) ====
@@ -178,7 +178,7 @@ tests/cases/compiler/capturedLetConstInLoop5.ts(229,13): error TS2367: This cond
             (() => x + v);
             if (x == 1) {
                 ~~~~~~
-!!! error TS2367: This condition will always return 'false' since the types '0' and '1' have no overlap.
+!!! error TS2367: Comparison of expressions of types '0' and '1' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.
                 return;
             }
         }
@@ -235,7 +235,7 @@ tests/cases/compiler/capturedLetConstInLoop5.ts(229,13): error TS2367: This cond
             (() => x + y + v);
             if (x == 1) {
                 ~~~~~~
-!!! error TS2367: This condition will always return 'false' since the types '0' and '1' have no overlap.
+!!! error TS2367: Comparison of expressions of types '0' and '1' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.
                 return;
             }
         }

tests/baselines/reference/capturedLetConstInLoop5_ES6.errors.txt

@@ -1,5 +1,5 @@
-tests/cases/compiler/capturedLetConstInLoop5_ES6.ts(174,13): error TS2367: This condition will always return 'false' since the types '0' and '1' have no overlap.
-tests/cases/compiler/capturedLetConstInLoop5_ES6.ts(229,13): error TS2367: This condition will always return 'false' since the types '0' and '1' have no overlap.
+tests/cases/compiler/capturedLetConstInLoop5_ES6.ts(174,13): error TS2367: Comparison of expressions of types '0' and '1' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.
+tests/cases/compiler/capturedLetConstInLoop5_ES6.ts(229,13): error TS2367: Comparison of expressions of types '0' and '1' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.
 
 
 ==== tests/cases/compiler/capturedLetConstInLoop5_ES6.ts (2 errors) ====
@@ -178,7 +178,7 @@ tests/cases/compiler/capturedLetConstInLoop5_ES6.ts(229,13): error TS2367: This
             (() => x + v);
             if (x == 1) {
                 ~~~~~~
-!!! error TS2367: This condition will always return 'false' since the types '0' and '1' have no overlap.
+!!! error TS2367: Comparison of expressions of types '0' and '1' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.
                 return;
             }
         }
@@ -235,7 +235,7 @@ tests/cases/compiler/capturedLetConstInLoop5_ES6.ts(229,13): error TS2367: This
             (() => x + y + v);
             if (x == 1) {
                 ~~~~~~
-!!! error TS2367: This condition will always return 'false' since the types '0' and '1' have no overlap.
+!!! error TS2367: Comparison of expressions of types '0' and '1' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.
                 return;
             }
         }

tests/baselines/reference/capturedLetConstInLoop6.errors.txt

@@ -1,7 +1,7 @@
-tests/cases/compiler/capturedLetConstInLoop6.ts(147,9): error TS2367: This condition will always return 'false' since the types '0' and '1' have no overlap.
-tests/cases/compiler/capturedLetConstInLoop6.ts(150,9): error TS2367: This condition will always return 'false' since the types '0' and '2' have no overlap.
-tests/cases/compiler/capturedLetConstInLoop6.ts(194,9): error TS2367: This condition will always return 'false' since the types '0' and '1' have no overlap.
-tests/cases/compiler/capturedLetConstInLoop6.ts(197,9): error TS2367: This condition will always return 'false' since the types '0' and '2' have no overlap.
+tests/cases/compiler/capturedLetConstInLoop6.ts(147,9): error TS2367: Comparison of expressions of types '0' and '1' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.
+tests/cases/compiler/capturedLetConstInLoop6.ts(150,9): error TS2367: Comparison of expressions of types '0' and '2' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.
+tests/cases/compiler/capturedLetConstInLoop6.ts(194,9): error TS2367: Comparison of expressions of types '0' and '1' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.
+tests/cases/compiler/capturedLetConstInLoop6.ts(197,9): error TS2367: Comparison of expressions of types '0' and '2' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.
 
 
 ==== tests/cases/compiler/capturedLetConstInLoop6.ts (4 errors) ====
@@ -153,12 +153,12 @@ tests/cases/compiler/capturedLetConstInLoop6.ts(197,9): error TS2367: This condi
         (() => x);
         if (x == 1) {
             ~~~~~~
-!!! error TS2367: This condition will always return 'false' since the types '0' and '1' have no overlap.
+!!! error TS2367: Comparison of expressions of types '0' and '1' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.
             break;
         }
         if (x == 2) {
             ~~~~~~
-!!! error TS2367: This condition will always return 'false' since the types '0' and '2' have no overlap.
+!!! error TS2367: Comparison of expressions of types '0' and '2' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.
             continue;
         }
     }
@@ -204,12 +204,12 @@ tests/cases/compiler/capturedLetConstInLoop6.ts(197,9): error TS2367: This condi
         (() => x + y);
         if (x == 1) {
             ~~~~~~
-!!! error TS2367: This condition will always return 'false' since the types '0' and '1' have no overlap.
+!!! error TS2367: Comparison of expressions of types '0' and '1' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.
             break;
         }
         if (x == 2) {
             ~~~~~~
-!!! error TS2367: This condition will always return 'false' since the types '0' and '2' have no overlap.
+!!! error TS2367: Comparison of expressions of types '0' and '2' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.
             continue;
         }
     }

tests/baselines/reference/capturedLetConstInLoop6_ES6.errors.txt

@@ -1,7 +1,7 @@
-tests/cases/compiler/capturedLetConstInLoop6_ES6.ts(147,9): error TS2367: This condition will always return 'false' since the types '0' and '1' have no overlap.
-tests/cases/compiler/capturedLetConstInLoop6_ES6.ts(150,9): error TS2367: This condition will always return 'false' since the types '0' and '2' have no overlap.
-tests/cases/compiler/capturedLetConstInLoop6_ES6.ts(194,9): error TS2367: This condition will always return 'false' since the types '0' and '1' have no overlap.
-tests/cases/compiler/capturedLetConstInLoop6_ES6.ts(197,9): error TS2367: This condition will always return 'false' since the types '0' and '2' have no overlap.
+tests/cases/compiler/capturedLetConstInLoop6_ES6.ts(147,9): error TS2367: Comparison of expressions of types '0' and '1' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.
+tests/cases/compiler/capturedLetConstInLoop6_ES6.ts(150,9): error TS2367: Comparison of expressions of types '0' and '2' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.
+tests/cases/compiler/capturedLetConstInLoop6_ES6.ts(194,9): error TS2367: Comparison of expressions of types '0' and '1' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.
+tests/cases/compiler/capturedLetConstInLoop6_ES6.ts(197,9): error TS2367: Comparison of expressions of types '0' and '2' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.
 
 
 ==== tests/cases/compiler/capturedLetConstInLoop6_ES6.ts (4 errors) ====
@@ -153,12 +153,12 @@ tests/cases/compiler/capturedLetConstInLoop6_ES6.ts(197,9): error TS2367: This c
         (() => x);
         if (x == 1) {
             ~~~~~~
-!!! error TS2367: This condition will always return 'false' since the types '0' and '1' have no overlap.
+!!! error TS2367: Comparison of expressions of types '0' and '1' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.
             break;
         }
         if (x == 2) {
             ~~~~~~
-!!! error TS2367: This condition will always return 'false' since the types '0' and '2' have no overlap.
+!!! error TS2367: Comparison of expressions of types '0' and '2' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.
             continue;
         }
     }
@@ -204,12 +204,12 @@ tests/cases/compiler/capturedLetConstInLoop6_ES6.ts(197,9): error TS2367: This c
         (() => x + y);
         if (x == 1) {
             ~~~~~~
-!!! error TS2367: This condition will always return 'false' since the types '0' and '1' have no overlap.
+!!! error TS2367: Comparison of expressions of types '0' and '1' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.
             break;
         }
         if (x == 2) {
             ~~~~~~
-!!! error TS2367: This condition will always return 'false' since the types '0' and '2' have no overlap.
+!!! error TS2367: Comparison of expressions of types '0' and '2' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert one of the expressions to 'unknown' first.
             continue;
         }
     }