diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index ecb8a3a928e5a..79efc447aa0f2 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -20041,7 +20041,8 @@ namespace ts {
             if (produceDiagnostics && targetType !== errorType) {
                 const widenedType = getWidenedType(exprType);
                 if (!isTypeComparableTo(targetType, widenedType)) {
-                    checkTypeComparableTo(exprType, targetType, errNode, Diagnostics.Type_0_cannot_be_converted_to_type_1);
+                    checkTypeComparableTo(exprType, targetType, errNode,
+                        Diagnostics.Conversion_of_type_0_to_type_1_may_be_a_mistake_because_neither_type_sufficiently_overlaps_with_the_other_If_this_was_intentional_convert_the_expression_to_unknown_first);
                 }
             }
             return targetType;
@@ -21515,7 +21516,7 @@ namespace ts {
             // in tagged templates.
             forEach(node.templateSpans, templateSpan => {
                 if (maybeTypeOfKind(checkExpression(templateSpan.expression), TypeFlags.ESSymbolLike)) {
-                    error(templateSpan.expression, Diagnostics.Type_0_cannot_be_converted_to_type_1, typeToString(esSymbolType), typeToString(stringType));
+                    error(templateSpan.expression, Diagnostics.Implicit_conversion_of_a_symbol_to_a_string_will_fail_at_runtime_Consider_wrapping_this_expression_in_String);
                 }
             });
 
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index a9118945b055c..1fa89c9d45f97 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -1196,7 +1196,7 @@
         "category": "Error",
         "code": 2351
     },
-    "Type '{0}' cannot be converted to type '{1}'.": {
+    "Conversion of type '{0}' to type '{1}' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.": {
         "category": "Error",
         "code": 2352
     },
@@ -2421,6 +2421,10 @@
         "category": "Error",
         "code": 2730
     },
+    "Implicit conversion of a 'symbol' to a 'string' will fail at runtime. Consider wrapping this expression in 'String(...)'.": {
+        "category": "Error",
+        "code": 2731
+    },
 
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",
diff --git a/tests/baselines/reference/arrayCast.errors.txt b/tests/baselines/reference/arrayCast.errors.txt
index 61463e5557b4c..ce9d031382514 100644
--- a/tests/baselines/reference/arrayCast.errors.txt
+++ b/tests/baselines/reference/arrayCast.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/compiler/arrayCast.ts(3,23): error TS2352: Type '{ foo: string; }[]' cannot be converted to type '{ id: number; }[]'.
+tests/cases/compiler/arrayCast.ts(3,23): error TS2352: Conversion of type '{ foo: string; }[]' to type '{ id: number; }[]' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Type '{ foo: string; }' is not comparable to type '{ id: number; }'.
     Object literal may only specify known properties, and 'foo' does not exist in type '{ id: number; }'.
 
@@ -8,7 +8,7 @@ tests/cases/compiler/arrayCast.ts(3,23): error TS2352: Type '{ foo: string; }[]'
     // has type { foo: string }[], which is not assignable to { id: number }[].
     <{ id: number; }[]>[{ foo: "s" }];
                           ~~~~~~~~
-!!! error TS2352: Type '{ foo: string; }[]' cannot be converted to type '{ id: number; }[]'.
+!!! error TS2352: Conversion of type '{ foo: string; }[]' to type '{ id: number; }[]' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Type '{ foo: string; }' is not comparable to type '{ id: number; }'.
 !!! error TS2352:     Object literal may only specify known properties, and 'foo' does not exist in type '{ id: number; }'.
     
diff --git a/tests/baselines/reference/asOperator2.errors.txt b/tests/baselines/reference/asOperator2.errors.txt
index 92603c25cb021..711c320ff7a1b 100644
--- a/tests/baselines/reference/asOperator2.errors.txt
+++ b/tests/baselines/reference/asOperator2.errors.txt
@@ -1,8 +1,8 @@
-tests/cases/conformance/expressions/asOperator/asOperator2.ts(1,9): error TS2352: Type 'number' cannot be converted to type 'string'.
+tests/cases/conformance/expressions/asOperator/asOperator2.ts(1,9): error TS2352: Conversion of type 'number' to type 'string' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 
 
 ==== tests/cases/conformance/expressions/asOperator/asOperator2.ts (1 errors) ====
     var x = 23 as string;
             ~~~~~~~~~~~~
-!!! error TS2352: Type 'number' cannot be converted to type 'string'.
+!!! error TS2352: Conversion of type 'number' to type 'string' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
     
\ No newline at end of file
diff --git a/tests/baselines/reference/asOperatorContextualType.errors.txt b/tests/baselines/reference/asOperatorContextualType.errors.txt
index 9431d6123e279..77ebe06fbf921 100644
--- a/tests/baselines/reference/asOperatorContextualType.errors.txt
+++ b/tests/baselines/reference/asOperatorContextualType.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/conformance/expressions/asOperator/asOperatorContextualType.ts(2,9): error TS2352: Type '(v: number) => number' cannot be converted to type '(x: number) => string'.
+tests/cases/conformance/expressions/asOperator/asOperatorContextualType.ts(2,9): error TS2352: Conversion of type '(v: number) => number' to type '(x: number) => string' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Type 'number' is not comparable to type 'string'.
 
 
@@ -6,5 +6,5 @@ tests/cases/conformance/expressions/asOperator/asOperatorContextualType.ts(2,9):
     // should error
     var x = (v => v) as (x: number) => string;
             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2352: Type '(v: number) => number' cannot be converted to type '(x: number) => string'.
+!!! error TS2352: Conversion of type '(v: number) => number' to type '(x: number) => string' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Type 'number' is not comparable to type 'string'.
\ No newline at end of file
diff --git a/tests/baselines/reference/asOperatorNames.errors.txt b/tests/baselines/reference/asOperatorNames.errors.txt
index 4f957791a24d3..c634a4a78873f 100644
--- a/tests/baselines/reference/asOperatorNames.errors.txt
+++ b/tests/baselines/reference/asOperatorNames.errors.txt
@@ -1,11 +1,11 @@
-tests/cases/conformance/expressions/asOperator/asOperatorNames.ts(2,9): error TS2352: Type 'number' cannot be converted to type 'string'.
+tests/cases/conformance/expressions/asOperator/asOperatorNames.ts(2,9): error TS2352: Conversion of type 'number' to type 'string' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 
 
 ==== tests/cases/conformance/expressions/asOperator/asOperatorNames.ts (1 errors) ====
     var a = 20;
     var b = a as string;
             ~~~~~~~~~~~
-!!! error TS2352: Type 'number' cannot be converted to type 'string'.
+!!! error TS2352: Conversion of type 'number' to type 'string' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
     var as = "hello";
     var as1 = as as string;
     
\ No newline at end of file
diff --git a/tests/baselines/reference/castingTuple.errors.txt b/tests/baselines/reference/castingTuple.errors.txt
index 344f403906d60..c7b00e2a0ca83 100644
--- a/tests/baselines/reference/castingTuple.errors.txt
+++ b/tests/baselines/reference/castingTuple.errors.txt
@@ -1,14 +1,14 @@
-tests/cases/conformance/types/tuple/castingTuple.ts(13,23): error TS2352: Type '[number, string]' cannot be converted to type '[number, string, boolean]'.
+tests/cases/conformance/types/tuple/castingTuple.ts(13,23): error TS2352: Conversion of type '[number, string]' to type '[number, string, boolean]' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Property '2' is missing in type '[number, string]'.
-tests/cases/conformance/types/tuple/castingTuple.ts(14,15): error TS2352: Type '[number, string, boolean]' cannot be converted to type '[number, string]'.
+tests/cases/conformance/types/tuple/castingTuple.ts(14,15): error TS2352: Conversion of type '[number, string, boolean]' to type '[number, string]' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Types of property 'length' are incompatible.
     Type '3' is not comparable to type '2'.
-tests/cases/conformance/types/tuple/castingTuple.ts(15,14): error TS2352: Type '[number, string]' cannot be converted to type '[number, string, boolean]'.
-tests/cases/conformance/types/tuple/castingTuple.ts(18,21): error TS2352: Type '[C, D]' cannot be converted to type '[C, D, A]'.
+tests/cases/conformance/types/tuple/castingTuple.ts(15,14): error TS2352: Conversion of type '[number, string]' to type '[number, string, boolean]' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
+tests/cases/conformance/types/tuple/castingTuple.ts(18,21): error TS2352: Conversion of type '[C, D]' to type '[C, D, A]' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Property '2' is missing in type '[C, D]'.
-tests/cases/conformance/types/tuple/castingTuple.ts(30,10): error TS2352: Type '[number, string]' cannot be converted to type '[number, number]'.
+tests/cases/conformance/types/tuple/castingTuple.ts(30,10): error TS2352: Conversion of type '[number, string]' to type '[number, number]' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Type 'string' is not comparable to type 'number'.
-tests/cases/conformance/types/tuple/castingTuple.ts(31,10): error TS2352: Type '[C, D]' cannot be converted to type '[A, I]'.
+tests/cases/conformance/types/tuple/castingTuple.ts(31,10): error TS2352: Conversion of type '[C, D]' to type '[A, I]' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Type 'C' is not comparable to type 'A'.
     Property 'a' is missing in type 'C'.
 tests/cases/conformance/types/tuple/castingTuple.ts(32,5): error TS2403: Subsequent variable declarations must have the same type.  Variable 'array1' must be of type '{}[]', but here has type 'number[]'.
@@ -30,21 +30,21 @@ tests/cases/conformance/types/tuple/castingTuple.ts(33,1): error TS2304: Cannot
     var emptyObjTuple = <[{}, {}]>numStrTuple;
     var numStrBoolTuple = <[number, string, boolean]>numStrTuple;
                           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2352: Type '[number, string]' cannot be converted to type '[number, string, boolean]'.
+!!! error TS2352: Conversion of type '[number, string]' to type '[number, string, boolean]' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Property '2' is missing in type '[number, string]'.
     var shorter = numStrBoolTuple as [number, string]
                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2352: Type '[number, string, boolean]' cannot be converted to type '[number, string]'.
+!!! error TS2352: Conversion of type '[number, string, boolean]' to type '[number, string]' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Types of property 'length' are incompatible.
 !!! error TS2352:     Type '3' is not comparable to type '2'.
     var longer = numStrTuple as [number, string, boolean]
                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2352: Type '[number, string]' cannot be converted to type '[number, string, boolean]'.
+!!! error TS2352: Conversion of type '[number, string]' to type '[number, string, boolean]' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
     var classCDTuple: [C, D] = [new C(), new D()];
     var interfaceIITuple = <[I, I]>classCDTuple;
     var classCDATuple = <[C, D, A]>classCDTuple;
                         ~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2352: Type '[C, D]' cannot be converted to type '[C, D, A]'.
+!!! error TS2352: Conversion of type '[C, D]' to type '[C, D, A]' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Property '2' is missing in type '[C, D]'.
     var eleFromCDA1 = classCDATuple[2]; // A
     var eleFromCDA2 = classCDATuple[5]; // C | D | A
@@ -59,11 +59,11 @@ tests/cases/conformance/types/tuple/castingTuple.ts(33,1): error TS2304: Cannot
     // error
     var t3 = <[number, number]>numStrTuple;
              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2352: Type '[number, string]' cannot be converted to type '[number, number]'.
+!!! error TS2352: Conversion of type '[number, string]' to type '[number, number]' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Type 'string' is not comparable to type 'number'.
     var t9 = <[A, I]>classCDTuple;
              ~~~~~~~~~~~~~~~~~~~~
-!!! error TS2352: Type '[C, D]' cannot be converted to type '[A, I]'.
+!!! error TS2352: Conversion of type '[C, D]' to type '[A, I]' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Type 'C' is not comparable to type 'A'.
 !!! error TS2352:     Property 'a' is missing in type 'C'.
     var array1 = <number[]>numStrTuple;
diff --git a/tests/baselines/reference/contextualTyping39.errors.txt b/tests/baselines/reference/contextualTyping39.errors.txt
index 9081480f4badf..5c399faeb62d2 100644
--- a/tests/baselines/reference/contextualTyping39.errors.txt
+++ b/tests/baselines/reference/contextualTyping39.errors.txt
@@ -1,9 +1,9 @@
-tests/cases/compiler/contextualTyping39.ts(1,11): error TS2352: Type '() => string' cannot be converted to type '() => number'.
+tests/cases/compiler/contextualTyping39.ts(1,11): error TS2352: Conversion of type '() => string' to type '() => number' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Type 'string' is not comparable to type 'number'.
 
 
 ==== tests/cases/compiler/contextualTyping39.ts (1 errors) ====
     var foo = <{ (): number; }> function() { return "err"; };
               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2352: Type '() => string' cannot be converted to type '() => number'.
+!!! error TS2352: Conversion of type '() => string' to type '() => number' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Type 'string' is not comparable to type 'number'.
\ No newline at end of file
diff --git a/tests/baselines/reference/contextualTyping41.errors.txt b/tests/baselines/reference/contextualTyping41.errors.txt
index 418d435e7fefc..afa94b8e33366 100644
--- a/tests/baselines/reference/contextualTyping41.errors.txt
+++ b/tests/baselines/reference/contextualTyping41.errors.txt
@@ -1,9 +1,9 @@
-tests/cases/compiler/contextualTyping41.ts(1,11): error TS2352: Type '() => string' cannot be converted to type '{ (): number; (i: number): number; }'.
+tests/cases/compiler/contextualTyping41.ts(1,11): error TS2352: Conversion of type '() => string' to type '{ (): number; (i: number): number; }' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Type 'string' is not comparable to type 'number'.
 
 
 ==== tests/cases/compiler/contextualTyping41.ts (1 errors) ====
     var foo = <{():number; (i:number):number; }> (function(){return "err";});
               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2352: Type '() => string' cannot be converted to type '{ (): number; (i: number): number; }'.
+!!! error TS2352: Conversion of type '() => string' to type '{ (): number; (i: number): number; }' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Type 'string' is not comparable to type 'number'.
\ No newline at end of file
diff --git a/tests/baselines/reference/defaultArgsInFunctionExpressions.errors.txt b/tests/baselines/reference/defaultArgsInFunctionExpressions.errors.txt
index d46963caeed8d..805f25d8dbcd6 100644
--- a/tests/baselines/reference/defaultArgsInFunctionExpressions.errors.txt
+++ b/tests/baselines/reference/defaultArgsInFunctionExpressions.errors.txt
@@ -2,9 +2,9 @@ tests/cases/compiler/defaultArgsInFunctionExpressions.ts(4,19): error TS2345: Ar
 tests/cases/compiler/defaultArgsInFunctionExpressions.ts(5,1): error TS2322: Type 'number' is not assignable to type 'string'.
 tests/cases/compiler/defaultArgsInFunctionExpressions.ts(8,20): error TS2322: Type '3' is not assignable to type 'string'.
 tests/cases/compiler/defaultArgsInFunctionExpressions.ts(11,1): error TS2322: Type 'string' is not assignable to type 'number'.
-tests/cases/compiler/defaultArgsInFunctionExpressions.ts(14,51): error TS2352: Type 'string' cannot be converted to type 'number'.
+tests/cases/compiler/defaultArgsInFunctionExpressions.ts(14,51): error TS2352: Conversion of type 'string' to type 'number' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 tests/cases/compiler/defaultArgsInFunctionExpressions.ts(17,41): error TS2322: Type '""' is not assignable to type 'number'.
-tests/cases/compiler/defaultArgsInFunctionExpressions.ts(20,62): error TS2352: Type 'string' cannot be converted to type 'number'.
+tests/cases/compiler/defaultArgsInFunctionExpressions.ts(20,62): error TS2352: Conversion of type 'string' to type 'number' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 tests/cases/compiler/defaultArgsInFunctionExpressions.ts(28,15): error TS2708: Cannot use namespace 'T' as a value.
 
 
@@ -32,7 +32,7 @@ tests/cases/compiler/defaultArgsInFunctionExpressions.ts(28,15): error TS2708: C
     // Contextually type the default arg with the type annotation
     var f3 = function (a: (s: string) => any = (s) => <number>s) { };
                                                       ~~~~~~~~~
-!!! error TS2352: Type 'string' cannot be converted to type 'number'.
+!!! error TS2352: Conversion of type 'string' to type 'number' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
     
     // Type check using the function's contextual type
     var f4: (a: number) => void = function (a = "") { };
@@ -42,7 +42,7 @@ tests/cases/compiler/defaultArgsInFunctionExpressions.ts(28,15): error TS2708: C
     // Contextually type the default arg using the function's contextual type
     var f5: (a: (s: string) => any) => void = function (a = s => <number>s) { };
                                                                  ~~~~~~~~~
-!!! error TS2352: Type 'string' cannot be converted to type 'number'.
+!!! error TS2352: Conversion of type 'string' to type 'number' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
     
     // Instantiated module
     module T { }
diff --git a/tests/baselines/reference/fuzzy.errors.txt b/tests/baselines/reference/fuzzy.errors.txt
index 173683297f983..879789e4b2351 100644
--- a/tests/baselines/reference/fuzzy.errors.txt
+++ b/tests/baselines/reference/fuzzy.errors.txt
@@ -2,7 +2,7 @@ tests/cases/compiler/fuzzy.ts(13,18): error TS2420: Class 'C' incorrectly implem
   Property 'alsoWorks' is missing in type 'C'.
 tests/cases/compiler/fuzzy.ts(21,34): error TS2322: Type 'this' is not assignable to type 'I'.
   Type 'C' is not assignable to type 'I'.
-tests/cases/compiler/fuzzy.ts(25,20): error TS2352: Type '{ oneI: this; }' cannot be converted to type 'R'.
+tests/cases/compiler/fuzzy.ts(25,20): error TS2352: Conversion of type '{ oneI: this; }' to type 'R' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Property 'anything' is missing in type '{ oneI: this; }'.
 
 
@@ -40,7 +40,7 @@ tests/cases/compiler/fuzzy.ts(25,20): error TS2352: Type '{ oneI: this; }' canno
             worksToo():R {
                 return <R>({ oneI: this });
                        ~~~~~~~~~~~~~~~~~~~
-!!! error TS2352: Type '{ oneI: this; }' cannot be converted to type 'R'.
+!!! error TS2352: Conversion of type '{ oneI: this; }' to type 'R' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Property 'anything' is missing in type '{ oneI: this; }'.
             }
         }
diff --git a/tests/baselines/reference/genericTypeAssertions1.errors.txt b/tests/baselines/reference/genericTypeAssertions1.errors.txt
index aa5f14f5da858..b4c7a165a9172 100644
--- a/tests/baselines/reference/genericTypeAssertions1.errors.txt
+++ b/tests/baselines/reference/genericTypeAssertions1.errors.txt
@@ -2,7 +2,7 @@ tests/cases/compiler/genericTypeAssertions1.ts(3,5): error TS2322: Type 'A<numbe
   Type 'number' is not assignable to type 'string'.
 tests/cases/compiler/genericTypeAssertions1.ts(4,5): error TS2322: Type 'A<A<number>>' is not assignable to type 'A<number>'.
   Type 'A<number>' is not assignable to type 'number'.
-tests/cases/compiler/genericTypeAssertions1.ts(4,21): error TS2352: Type 'A<number>' cannot be converted to type 'A<A<number>>'.
+tests/cases/compiler/genericTypeAssertions1.ts(4,21): error TS2352: Conversion of type 'A<number>' to type 'A<A<number>>' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Type 'number' is not comparable to type 'A<number>'.
 
 
@@ -18,5 +18,5 @@ tests/cases/compiler/genericTypeAssertions1.ts(4,21): error TS2352: Type 'A<numb
 !!! error TS2322: Type 'A<A<number>>' is not assignable to type 'A<number>'.
 !!! error TS2322:   Type 'A<number>' is not assignable to type 'number'.
                         ~~~~~~~~~~~~~~~~~
-!!! error TS2352: Type 'A<number>' cannot be converted to type 'A<A<number>>'.
+!!! error TS2352: Conversion of type 'A<number>' to type 'A<A<number>>' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Type 'number' is not comparable to type 'A<number>'.
\ No newline at end of file
diff --git a/tests/baselines/reference/genericTypeAssertions2.errors.txt b/tests/baselines/reference/genericTypeAssertions2.errors.txt
index 756690f178378..df3093cbc8ad9 100644
--- a/tests/baselines/reference/genericTypeAssertions2.errors.txt
+++ b/tests/baselines/reference/genericTypeAssertions2.errors.txt
@@ -5,7 +5,7 @@ tests/cases/compiler/genericTypeAssertions2.ts(10,5): error TS2322: Type 'B<stri
         Type 'number' is not assignable to type 'string'.
 tests/cases/compiler/genericTypeAssertions2.ts(11,5): error TS2322: Type 'A<number>' is not assignable to type 'B<number>'.
   Property 'bar' is missing in type 'A<number>'.
-tests/cases/compiler/genericTypeAssertions2.ts(13,21): error TS2352: Type 'undefined[]' cannot be converted to type 'A<number>'.
+tests/cases/compiler/genericTypeAssertions2.ts(13,21): error TS2352: Conversion of type 'undefined[]' to type 'A<number>' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Property 'foo' is missing in type 'undefined[]'.
 
 
@@ -33,5 +33,5 @@ tests/cases/compiler/genericTypeAssertions2.ts(13,21): error TS2352: Type 'undef
     var r4: A<number> = <A<number>>new A();
     var r5: A<number> = <A<number>>[]; // error
                         ~~~~~~~~~~~~~
-!!! error TS2352: Type 'undefined[]' cannot be converted to type 'A<number>'.
+!!! error TS2352: Conversion of type 'undefined[]' to type 'A<number>' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Property 'foo' is missing in type 'undefined[]'.
\ No newline at end of file
diff --git a/tests/baselines/reference/genericTypeAssertions4.errors.txt b/tests/baselines/reference/genericTypeAssertions4.errors.txt
index 401834930f30f..4c23bd6d4585b 100644
--- a/tests/baselines/reference/genericTypeAssertions4.errors.txt
+++ b/tests/baselines/reference/genericTypeAssertions4.errors.txt
@@ -1,8 +1,8 @@
 tests/cases/compiler/genericTypeAssertions4.ts(19,5): error TS2322: Type 'A' is not assignable to type 'T'.
 tests/cases/compiler/genericTypeAssertions4.ts(20,5): error TS2322: Type 'B' is not assignable to type 'T'.
 tests/cases/compiler/genericTypeAssertions4.ts(21,5): error TS2322: Type 'C' is not assignable to type 'T'.
-tests/cases/compiler/genericTypeAssertions4.ts(23,9): error TS2352: Type 'B' cannot be converted to type 'T'.
-tests/cases/compiler/genericTypeAssertions4.ts(24,9): error TS2352: Type 'C' cannot be converted to type 'T'.
+tests/cases/compiler/genericTypeAssertions4.ts(23,9): error TS2352: Conversion of type 'B' to type 'T' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
+tests/cases/compiler/genericTypeAssertions4.ts(24,9): error TS2352: Conversion of type 'C' to type 'T' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 
 
 ==== tests/cases/compiler/genericTypeAssertions4.ts (5 errors) ====
@@ -36,8 +36,8 @@ tests/cases/compiler/genericTypeAssertions4.ts(24,9): error TS2352: Type 'C' can
         y = <T>a;
         y = <T>b; // error: cannot convert B to T
             ~~~~
-!!! error TS2352: Type 'B' cannot be converted to type 'T'.
+!!! error TS2352: Conversion of type 'B' to type 'T' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
         y = <T>c; // error: cannot convert C to T
             ~~~~
-!!! error TS2352: Type 'C' cannot be converted to type 'T'.
+!!! error TS2352: Conversion of type 'C' to type 'T' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/genericTypeAssertions5.errors.txt b/tests/baselines/reference/genericTypeAssertions5.errors.txt
index 45f7607336385..e01b90d72a5f8 100644
--- a/tests/baselines/reference/genericTypeAssertions5.errors.txt
+++ b/tests/baselines/reference/genericTypeAssertions5.errors.txt
@@ -1,8 +1,8 @@
 tests/cases/compiler/genericTypeAssertions5.ts(19,5): error TS2322: Type 'A' is not assignable to type 'T'.
 tests/cases/compiler/genericTypeAssertions5.ts(20,5): error TS2322: Type 'B' is not assignable to type 'T'.
 tests/cases/compiler/genericTypeAssertions5.ts(21,5): error TS2322: Type 'C' is not assignable to type 'T'.
-tests/cases/compiler/genericTypeAssertions5.ts(23,9): error TS2352: Type 'B' cannot be converted to type 'T'.
-tests/cases/compiler/genericTypeAssertions5.ts(24,9): error TS2352: Type 'C' cannot be converted to type 'T'.
+tests/cases/compiler/genericTypeAssertions5.ts(23,9): error TS2352: Conversion of type 'B' to type 'T' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
+tests/cases/compiler/genericTypeAssertions5.ts(24,9): error TS2352: Conversion of type 'C' to type 'T' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 
 
 ==== tests/cases/compiler/genericTypeAssertions5.ts (5 errors) ====
@@ -36,8 +36,8 @@ tests/cases/compiler/genericTypeAssertions5.ts(24,9): error TS2352: Type 'C' can
         y = <T>a;
         y = <T>b; // error: cannot convert B to T
             ~~~~
-!!! error TS2352: Type 'B' cannot be converted to type 'T'.
+!!! error TS2352: Conversion of type 'B' to type 'T' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
         y = <T>c; // error: cannot convert C to T
             ~~~~
-!!! error TS2352: Type 'C' cannot be converted to type 'T'.
+!!! error TS2352: Conversion of type 'C' to type 'T' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/genericTypeAssertions6.errors.txt b/tests/baselines/reference/genericTypeAssertions6.errors.txt
index 1bda683b88a23..ef65803a47d98 100644
--- a/tests/baselines/reference/genericTypeAssertions6.errors.txt
+++ b/tests/baselines/reference/genericTypeAssertions6.errors.txt
@@ -1,6 +1,6 @@
-tests/cases/compiler/genericTypeAssertions6.ts(8,13): error TS2352: Type 'U' cannot be converted to type 'T'.
-tests/cases/compiler/genericTypeAssertions6.ts(9,13): error TS2352: Type 'T' cannot be converted to type 'U'.
-tests/cases/compiler/genericTypeAssertions6.ts(19,17): error TS2352: Type 'U' cannot be converted to type 'T'.
+tests/cases/compiler/genericTypeAssertions6.ts(8,13): error TS2352: Conversion of type 'U' to type 'T' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
+tests/cases/compiler/genericTypeAssertions6.ts(9,13): error TS2352: Conversion of type 'T' to type 'U' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
+tests/cases/compiler/genericTypeAssertions6.ts(19,17): error TS2352: Conversion of type 'U' to type 'T' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Type 'Date' is not comparable to type 'T'.
 
 
@@ -14,10 +14,10 @@ tests/cases/compiler/genericTypeAssertions6.ts(19,17): error TS2352: Type 'U' ca
         f(x: T, y: U) {
             x = <T>y;
                 ~~~~
-!!! error TS2352: Type 'U' cannot be converted to type 'T'.
+!!! error TS2352: Conversion of type 'U' to type 'T' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
             y = <U>x;
                 ~~~~
-!!! error TS2352: Type 'T' cannot be converted to type 'U'.
+!!! error TS2352: Conversion of type 'T' to type 'U' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
         }
     }
     
@@ -29,7 +29,7 @@ tests/cases/compiler/genericTypeAssertions6.ts(19,17): error TS2352: Type 'U' ca
             var d = <U>new Date();
             var e = <T><U>new Date();
                     ~~~~~~~~~~~~~~~~
-!!! error TS2352: Type 'U' cannot be converted to type 'T'.
+!!! error TS2352: Conversion of type 'U' to type 'T' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Type 'Date' is not comparable to type 'T'.
         }
     }
diff --git a/tests/baselines/reference/importCallExpressionCheckReturntype1.errors.txt b/tests/baselines/reference/importCallExpressionCheckReturntype1.errors.txt
index c62c7868e10be..89a1724ea9aa5 100644
--- a/tests/baselines/reference/importCallExpressionCheckReturntype1.errors.txt
+++ b/tests/baselines/reference/importCallExpressionCheckReturntype1.errors.txt
@@ -1,7 +1,7 @@
 tests/cases/conformance/dynamicImport/1.ts(4,5): error TS2322: Type 'Promise<typeof import("tests/cases/conformance/dynamicImport/defaultPath")>' is not assignable to type 'Promise<typeof import("tests/cases/conformance/dynamicImport/anotherModule")>'.
   Type 'typeof import("tests/cases/conformance/dynamicImport/defaultPath")' is not assignable to type 'typeof import("tests/cases/conformance/dynamicImport/anotherModule")'.
     Property 'D' is missing in type 'typeof import("tests/cases/conformance/dynamicImport/defaultPath")'.
-tests/cases/conformance/dynamicImport/1.ts(5,10): error TS2352: Type 'Promise<typeof import("tests/cases/conformance/dynamicImport/defaultPath")>' cannot be converted to type 'Promise<typeof import("tests/cases/conformance/dynamicImport/anotherModule")>'.
+tests/cases/conformance/dynamicImport/1.ts(5,10): error TS2352: Conversion of type 'Promise<typeof import("tests/cases/conformance/dynamicImport/defaultPath")>' to type 'Promise<typeof import("tests/cases/conformance/dynamicImport/anotherModule")>' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Type 'typeof import("tests/cases/conformance/dynamicImport/defaultPath")' is not comparable to type 'typeof import("tests/cases/conformance/dynamicImport/anotherModule")'.
     Property 'D' is missing in type 'typeof import("tests/cases/conformance/dynamicImport/defaultPath")'.
 
@@ -23,7 +23,7 @@ tests/cases/conformance/dynamicImport/1.ts(5,10): error TS2352: Type 'Promise<ty
 !!! error TS2322:     Property 'D' is missing in type 'typeof import("tests/cases/conformance/dynamicImport/defaultPath")'.
     let p2 = import("./defaultPath") as Promise<typeof anotherModule>;
              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2352: Type 'Promise<typeof import("tests/cases/conformance/dynamicImport/defaultPath")>' cannot be converted to type 'Promise<typeof import("tests/cases/conformance/dynamicImport/anotherModule")>'.
+!!! error TS2352: Conversion of type 'Promise<typeof import("tests/cases/conformance/dynamicImport/defaultPath")>' to type 'Promise<typeof import("tests/cases/conformance/dynamicImport/anotherModule")>' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Type 'typeof import("tests/cases/conformance/dynamicImport/defaultPath")' is not comparable to type 'typeof import("tests/cases/conformance/dynamicImport/anotherModule")'.
 !!! error TS2352:     Property 'D' is missing in type 'typeof import("tests/cases/conformance/dynamicImport/defaultPath")'.
     let p3: Promise<any> = import("./defaultPath");
diff --git a/tests/baselines/reference/intTypeCheck.errors.txt b/tests/baselines/reference/intTypeCheck.errors.txt
index e5fbfbdbee850..5b7ca138339b8 100644
--- a/tests/baselines/reference/intTypeCheck.errors.txt
+++ b/tests/baselines/reference/intTypeCheck.errors.txt
@@ -76,7 +76,7 @@ tests/cases/compiler/intTypeCheck.ts(182,5): error TS2322: Type '{}' is not assi
 tests/cases/compiler/intTypeCheck.ts(183,5): error TS2322: Type 'Object' is not assignable to type 'i7'.
   The 'Object' type is assignable to very few other types. Did you mean to use the 'any' type instead?
     Type 'Object' provides no match for the signature 'new (): any'.
-tests/cases/compiler/intTypeCheck.ts(185,17): error TS2352: Type 'Base' cannot be converted to type 'i7'.
+tests/cases/compiler/intTypeCheck.ts(185,17): error TS2352: Conversion of type 'Base' to type 'i7' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Type 'Base' provides no match for the signature 'new (): any'.
 tests/cases/compiler/intTypeCheck.ts(187,5): error TS2322: Type '() => void' is not assignable to type 'i7'.
   Type '() => void' provides no match for the signature 'new (): any'.
@@ -408,7 +408,7 @@ tests/cases/compiler/intTypeCheck.ts(205,17): error TS2351: Cannot use 'new' wit
     var obj69: i7 = new obj66;
     var obj70: i7 = <i7>new Base;
                     ~~~~~~~~~~~~
-!!! error TS2352: Type 'Base' cannot be converted to type 'i7'.
+!!! error TS2352: Conversion of type 'Base' to type 'i7' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Type 'Base' provides no match for the signature 'new (): any'.
     var obj71: i7 = null;
     var obj72: i7 = function () { };
diff --git a/tests/baselines/reference/jsdocTypeTagCast.errors.txt b/tests/baselines/reference/jsdocTypeTagCast.errors.txt
index 8cbe096de3594..a84d31a341b7c 100644
--- a/tests/baselines/reference/jsdocTypeTagCast.errors.txt
+++ b/tests/baselines/reference/jsdocTypeTagCast.errors.txt
@@ -1,17 +1,17 @@
-tests/cases/conformance/jsdoc/b.js(4,13): error TS2352: Type 'number' cannot be converted to type 'string'.
-tests/cases/conformance/jsdoc/b.js(45,16): error TS2352: Type 'SomeOther' cannot be converted to type 'SomeBase'.
+tests/cases/conformance/jsdoc/b.js(4,13): error TS2352: Conversion of type 'number' to type 'string' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
+tests/cases/conformance/jsdoc/b.js(45,16): error TS2352: Conversion of type 'SomeOther' to type 'SomeBase' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Property 'p' is missing in type 'SomeOther'.
-tests/cases/conformance/jsdoc/b.js(49,19): error TS2352: Type 'SomeOther' cannot be converted to type 'SomeDerived'.
+tests/cases/conformance/jsdoc/b.js(49,19): error TS2352: Conversion of type 'SomeOther' to type 'SomeDerived' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Property 'x' is missing in type 'SomeOther'.
-tests/cases/conformance/jsdoc/b.js(51,17): error TS2352: Type 'SomeDerived' cannot be converted to type 'SomeOther'.
+tests/cases/conformance/jsdoc/b.js(51,17): error TS2352: Conversion of type 'SomeDerived' to type 'SomeOther' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Property 'q' is missing in type 'SomeDerived'.
-tests/cases/conformance/jsdoc/b.js(52,17): error TS2352: Type 'SomeBase' cannot be converted to type 'SomeOther'.
+tests/cases/conformance/jsdoc/b.js(52,17): error TS2352: Conversion of type 'SomeBase' to type 'SomeOther' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Property 'q' is missing in type 'SomeBase'.
 tests/cases/conformance/jsdoc/b.js(58,1): error TS2322: Type 'SomeFakeClass' is not assignable to type 'SomeBase'.
   Types of property 'p' are incompatible.
     Type 'string | number' is not assignable to type 'number'.
       Type 'string' is not assignable to type 'number'.
-tests/cases/conformance/jsdoc/b.js(66,8): error TS2352: Type 'boolean' cannot be converted to type 'string | number'.
+tests/cases/conformance/jsdoc/b.js(66,8): error TS2352: Conversion of type 'boolean' to type 'string | number' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 tests/cases/conformance/jsdoc/b.js(66,15): error TS2304: Cannot find name 'numOrStr'.
 tests/cases/conformance/jsdoc/b.js(66,24): error TS1005: '}' expected.
 tests/cases/conformance/jsdoc/b.js(66,38): error TS2454: Variable 'numOrStr' is used before being assigned.
@@ -29,7 +29,7 @@ tests/cases/conformance/jsdoc/b.js(67,8): error TS2454: Variable 'numOrStr' is u
     
     var W = /** @type {string} */(4); // Error
                 ~~~~~~~~~~~~~~
-!!! error TS2352: Type 'number' cannot be converted to type 'string'.
+!!! error TS2352: Conversion of type 'number' to type 'string' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
     
     /** @type {*} */
     var a;
@@ -72,23 +72,23 @@ tests/cases/conformance/jsdoc/b.js(67,8): error TS2454: Variable 'numOrStr' is u
     someBase = /** @type {SomeBase} */(someBase);
     someBase = /** @type {SomeBase} */(someOther); // Error
                    ~~~~~~~~~~~~~~~~
-!!! error TS2352: Type 'SomeOther' cannot be converted to type 'SomeBase'.
+!!! error TS2352: Conversion of type 'SomeOther' to type 'SomeBase' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Property 'p' is missing in type 'SomeOther'.
     
     someDerived = /** @type {SomeDerived} */(someDerived);
     someDerived = /** @type {SomeDerived} */(someBase);
     someDerived = /** @type {SomeDerived} */(someOther); // Error
                       ~~~~~~~~~~~~~~~~~~~
-!!! error TS2352: Type 'SomeOther' cannot be converted to type 'SomeDerived'.
+!!! error TS2352: Conversion of type 'SomeOther' to type 'SomeDerived' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Property 'x' is missing in type 'SomeOther'.
     
     someOther = /** @type {SomeOther} */(someDerived); // Error
                     ~~~~~~~~~~~~~~~~~
-!!! error TS2352: Type 'SomeDerived' cannot be converted to type 'SomeOther'.
+!!! error TS2352: Conversion of type 'SomeDerived' to type 'SomeOther' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Property 'q' is missing in type 'SomeDerived'.
     someOther = /** @type {SomeOther} */(someBase); // Error
                     ~~~~~~~~~~~~~~~~~
-!!! error TS2352: Type 'SomeBase' cannot be converted to type 'SomeOther'.
+!!! error TS2352: Conversion of type 'SomeBase' to type 'SomeOther' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Property 'q' is missing in type 'SomeBase'.
     someOther = /** @type {SomeOther} */(someOther);
     
@@ -110,7 +110,7 @@ tests/cases/conformance/jsdoc/b.js(67,8): error TS2454: Variable 'numOrStr' is u
     var str;
     if(/** @type {numOrStr is string} */(numOrStr === undefined)) { // Error
            ~~~~~~~~~~~~~~~
-!!! error TS2352: Type 'boolean' cannot be converted to type 'string | number'.
+!!! error TS2352: Conversion of type 'boolean' to type 'string | number' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
                   ~~~~~~~~
 !!! error TS2304: Cannot find name 'numOrStr'.
                            ~~
diff --git a/tests/baselines/reference/literals-negative.errors.txt b/tests/baselines/reference/literals-negative.errors.txt
index 2024066d9f264..18ac3c27141c7 100644
--- a/tests/baselines/reference/literals-negative.errors.txt
+++ b/tests/baselines/reference/literals-negative.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/compiler/literals-negative.ts(5,9): error TS2352: Type 'number' cannot be converted to type 'boolean'.
+tests/cases/compiler/literals-negative.ts(5,9): error TS2352: Conversion of type 'number' to type 'boolean' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 
 
 ==== tests/cases/compiler/literals-negative.ts (1 errors) ====
@@ -8,7 +8,7 @@ tests/cases/compiler/literals-negative.ts(5,9): error TS2352: Type 'number' cann
     var s = <string>(null);
     var b = <boolean>(n);
             ~~~~~~~~~~~~
-!!! error TS2352: Type 'number' cannot be converted to type 'boolean'.
+!!! error TS2352: Conversion of type 'number' to type 'boolean' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
     
     function isVoid() : void { }
     
diff --git a/tests/baselines/reference/noImplicitAnyInCastExpression.errors.txt b/tests/baselines/reference/noImplicitAnyInCastExpression.errors.txt
index 769353b996582..3f30b649c9687 100644
--- a/tests/baselines/reference/noImplicitAnyInCastExpression.errors.txt
+++ b/tests/baselines/reference/noImplicitAnyInCastExpression.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/compiler/noImplicitAnyInCastExpression.ts(15,2): error TS2352: Type '{ c: null; }' cannot be converted to type 'IFoo'.
+tests/cases/compiler/noImplicitAnyInCastExpression.ts(15,2): error TS2352: Conversion of type '{ c: null; }' to type 'IFoo' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Property 'a' is missing in type '{ c: null; }'.
 
 
@@ -19,5 +19,5 @@ tests/cases/compiler/noImplicitAnyInCastExpression.ts(15,2): error TS2352: Type
     // Neither types is assignable to each other
     (<IFoo>{ c: null });
      ~~~~~~~~~~~~~~~~~
-!!! error TS2352: Type '{ c: null; }' cannot be converted to type 'IFoo'.
+!!! error TS2352: Conversion of type '{ c: null; }' to type 'IFoo' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Property 'a' is missing in type '{ c: null; }'.
\ No newline at end of file
diff --git a/tests/baselines/reference/noImplicitSymbolToString.errors.txt b/tests/baselines/reference/noImplicitSymbolToString.errors.txt
index 6dae5c5d76f45..cb664d9a8b93e 100644
--- a/tests/baselines/reference/noImplicitSymbolToString.errors.txt
+++ b/tests/baselines/reference/noImplicitSymbolToString.errors.txt
@@ -1,8 +1,8 @@
-tests/cases/compiler/noImplicitSymbolToString.ts(6,30): error TS2352: Type 'symbol' cannot be converted to type 'string'.
+tests/cases/compiler/noImplicitSymbolToString.ts(6,30): error TS2731: Implicit conversion of a 'symbol' to a 'string' will fail at runtime. Consider wrapping this expression in 'String(...)'.
 tests/cases/compiler/noImplicitSymbolToString.ts(7,30): error TS2469: The '+' operator cannot be applied to type 'symbol'.
 tests/cases/compiler/noImplicitSymbolToString.ts(8,8): error TS2469: The '+=' operator cannot be applied to type 'symbol'.
-tests/cases/compiler/noImplicitSymbolToString.ts(13,47): error TS2352: Type 'symbol' cannot be converted to type 'string'.
-tests/cases/compiler/noImplicitSymbolToString.ts(13,90): error TS2352: Type 'symbol' cannot be converted to type 'string'.
+tests/cases/compiler/noImplicitSymbolToString.ts(13,47): error TS2731: Implicit conversion of a 'symbol' to a 'string' will fail at runtime. Consider wrapping this expression in 'String(...)'.
+tests/cases/compiler/noImplicitSymbolToString.ts(13,90): error TS2731: Implicit conversion of a 'symbol' to a 'string' will fail at runtime. Consider wrapping this expression in 'String(...)'.
 
 
 ==== tests/cases/compiler/noImplicitSymbolToString.ts (5 errors) ====
@@ -13,7 +13,7 @@ tests/cases/compiler/noImplicitSymbolToString.ts(13,90): error TS2352: Type 'sym
     
     const templateStr = `hello ${symbol}`;
                                  ~~~~~~
-!!! error TS2352: Type 'symbol' cannot be converted to type 'string'.
+!!! error TS2731: Implicit conversion of a 'symbol' to a 'string' will fail at runtime. Consider wrapping this expression in 'String(...)'.
     const appendStr = "hello " + symbol;
                                  ~~~~~~
 !!! error TS2469: The '+' operator cannot be applied to type 'symbol'.
@@ -26,7 +26,7 @@ tests/cases/compiler/noImplicitSymbolToString.ts(13,90): error TS2352: Type 'sym
     
     const templateStrUnion = `union with number ${symbolUnionNumber} and union with string ${symbolUnionString}`;
                                                   ~~~~~~~~~~~~~~~~~
-!!! error TS2352: Type 'symbol' cannot be converted to type 'string'.
+!!! error TS2731: Implicit conversion of a 'symbol' to a 'string' will fail at runtime. Consider wrapping this expression in 'String(...)'.
                                                                                              ~~~~~~~~~~~~~~~~~
-!!! error TS2352: Type 'symbol' cannot be converted to type 'string'.
+!!! error TS2731: Implicit conversion of a 'symbol' to a 'string' will fail at runtime. Consider wrapping this expression in 'String(...)'.
     
\ No newline at end of file
diff --git a/tests/baselines/reference/objectTypesIdentityWithPrivates3.errors.txt b/tests/baselines/reference/objectTypesIdentityWithPrivates3.errors.txt
index 2342065605be9..983548016e8b9 100644
--- a/tests/baselines/reference/objectTypesIdentityWithPrivates3.errors.txt
+++ b/tests/baselines/reference/objectTypesIdentityWithPrivates3.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/conformance/types/typeRelationships/typeAndMemberIdentity/objectTypesIdentityWithPrivates3.ts(25,1): error TS2352: Type 'C3<T2>' cannot be converted to type 'C4'.
+tests/cases/conformance/types/typeRelationships/typeAndMemberIdentity/objectTypesIdentityWithPrivates3.ts(25,1): error TS2352: Conversion of type 'C3<T2>' to type 'C4' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Property 'y' is missing in type 'C3<T2>'.
 
 
@@ -29,5 +29,5 @@ tests/cases/conformance/types/typeRelationships/typeAndMemberIdentity/objectType
     var c3: C3<T2>;
     <C4>c3; // Should fail (private x originates in the same declaration, but different types)
     ~~~~~~
-!!! error TS2352: Type 'C3<T2>' cannot be converted to type 'C4'.
+!!! error TS2352: Conversion of type 'C3<T2>' to type 'C4' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Property 'y' is missing in type 'C3<T2>'.
\ No newline at end of file
diff --git a/tests/baselines/reference/stringLiteralsAssertionsInEqualityComparisons02.errors.txt b/tests/baselines/reference/stringLiteralsAssertionsInEqualityComparisons02.errors.txt
index c03b08bd0ac1b..8cb9e8203e7ad 100644
--- a/tests/baselines/reference/stringLiteralsAssertionsInEqualityComparisons02.errors.txt
+++ b/tests/baselines/reference/stringLiteralsAssertionsInEqualityComparisons02.errors.txt
@@ -1,6 +1,6 @@
 tests/cases/conformance/types/literal/stringLiteralsAssertionsInEqualityComparisons02.ts(3,9): error TS2367: This condition will always return 'false' since the types '"foo"' and '"baz"' have no overlap.
 tests/cases/conformance/types/literal/stringLiteralsAssertionsInEqualityComparisons02.ts(5,9): error TS2367: This condition will always return 'false' since the types 'string' and 'number' have no overlap.
-tests/cases/conformance/types/literal/stringLiteralsAssertionsInEqualityComparisons02.ts(5,19): error TS2352: Type 'string' cannot be converted to type 'number'.
+tests/cases/conformance/types/literal/stringLiteralsAssertionsInEqualityComparisons02.ts(5,19): error TS2352: Conversion of type 'string' to type 'number' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 
 
 ==== tests/cases/conformance/types/literal/stringLiteralsAssertionsInEqualityComparisons02.ts (3 errors) ====
@@ -14,5 +14,5 @@ tests/cases/conformance/types/literal/stringLiteralsAssertionsInEqualityComparis
             ~~~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS2367: This condition will always return 'false' since the types 'string' and 'number' have no overlap.
                       ~~~~~~~~~~~~~
-!!! error TS2352: Type 'string' cannot be converted to type 'number'.
+!!! error TS2352: Conversion of type 'string' to type 'number' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
     var d = "foo" === ("bar" as EnhancedString);
\ No newline at end of file
diff --git a/tests/baselines/reference/typeAssertions.errors.txt b/tests/baselines/reference/typeAssertions.errors.txt
index cefc15b8e23bc..ad6065b0755c7 100644
--- a/tests/baselines/reference/typeAssertions.errors.txt
+++ b/tests/baselines/reference/typeAssertions.errors.txt
@@ -1,11 +1,11 @@
 tests/cases/conformance/expressions/typeAssertions/typeAssertions.ts(5,9): error TS2558: Expected 0 type arguments, but got 1.
-tests/cases/conformance/expressions/typeAssertions/typeAssertions.ts(31,12): error TS2352: Type 'SomeOther' cannot be converted to type 'SomeBase'.
+tests/cases/conformance/expressions/typeAssertions/typeAssertions.ts(31,12): error TS2352: Conversion of type 'SomeOther' to type 'SomeBase' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Property 'p' is missing in type 'SomeOther'.
-tests/cases/conformance/expressions/typeAssertions/typeAssertions.ts(35,15): error TS2352: Type 'SomeOther' cannot be converted to type 'SomeDerived'.
+tests/cases/conformance/expressions/typeAssertions/typeAssertions.ts(35,15): error TS2352: Conversion of type 'SomeOther' to type 'SomeDerived' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Property 'x' is missing in type 'SomeOther'.
-tests/cases/conformance/expressions/typeAssertions/typeAssertions.ts(37,13): error TS2352: Type 'SomeDerived' cannot be converted to type 'SomeOther'.
+tests/cases/conformance/expressions/typeAssertions/typeAssertions.ts(37,13): error TS2352: Conversion of type 'SomeDerived' to type 'SomeOther' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Property 'q' is missing in type 'SomeDerived'.
-tests/cases/conformance/expressions/typeAssertions/typeAssertions.ts(38,13): error TS2352: Type 'SomeBase' cannot be converted to type 'SomeOther'.
+tests/cases/conformance/expressions/typeAssertions/typeAssertions.ts(38,13): error TS2352: Conversion of type 'SomeBase' to type 'SomeOther' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Property 'q' is missing in type 'SomeBase'.
 tests/cases/conformance/expressions/typeAssertions/typeAssertions.ts(44,5): error TS2304: Cannot find name 'numOrStr'.
 tests/cases/conformance/expressions/typeAssertions/typeAssertions.ts(44,14): error TS1005: '>' expected.
@@ -58,23 +58,23 @@ tests/cases/conformance/expressions/typeAssertions/typeAssertions.ts(48,50): err
     someBase = <SomeBase>someBase;
     someBase = <SomeBase>someOther; // Error
                ~~~~~~~~~~~~~~~~~~~
-!!! error TS2352: Type 'SomeOther' cannot be converted to type 'SomeBase'.
+!!! error TS2352: Conversion of type 'SomeOther' to type 'SomeBase' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Property 'p' is missing in type 'SomeOther'.
     
     someDerived = <SomeDerived>someDerived;
     someDerived = <SomeDerived>someBase;
     someDerived = <SomeDerived>someOther; // Error
                   ~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2352: Type 'SomeOther' cannot be converted to type 'SomeDerived'.
+!!! error TS2352: Conversion of type 'SomeOther' to type 'SomeDerived' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Property 'x' is missing in type 'SomeOther'.
     
     someOther = <SomeOther>someDerived; // Error
                 ~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2352: Type 'SomeDerived' cannot be converted to type 'SomeOther'.
+!!! error TS2352: Conversion of type 'SomeDerived' to type 'SomeOther' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Property 'q' is missing in type 'SomeDerived'.
     someOther = <SomeOther>someBase; // Error
                 ~~~~~~~~~~~~~~~~~~~
-!!! error TS2352: Type 'SomeBase' cannot be converted to type 'SomeOther'.
+!!! error TS2352: Conversion of type 'SomeBase' to type 'SomeOther' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Property 'q' is missing in type 'SomeBase'.
     someOther = <SomeOther>someOther;
     
diff --git a/tests/baselines/reference/typeAssertionsWithIntersectionTypes01.errors.txt b/tests/baselines/reference/typeAssertionsWithIntersectionTypes01.errors.txt
index 42ed640e8fc29..16a2a726915ef 100644
--- a/tests/baselines/reference/typeAssertionsWithIntersectionTypes01.errors.txt
+++ b/tests/baselines/reference/typeAssertionsWithIntersectionTypes01.errors.txt
@@ -1,7 +1,7 @@
-tests/cases/conformance/types/typeRelationships/comparable/typeAssertionsWithIntersectionTypes01.ts(17,9): error TS2352: Type 'I2' cannot be converted to type 'I1 & I3'.
+tests/cases/conformance/types/typeRelationships/comparable/typeAssertionsWithIntersectionTypes01.ts(17,9): error TS2352: Conversion of type 'I2' to type 'I1 & I3' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
   Type 'I2' is not comparable to type 'I3'.
     Property 'p3' is missing in type 'I2'.
-tests/cases/conformance/types/typeRelationships/comparable/typeAssertionsWithIntersectionTypes01.ts(18,9): error TS2352: Type 'I2' cannot be converted to type 'I3'.
+tests/cases/conformance/types/typeRelationships/comparable/typeAssertionsWithIntersectionTypes01.ts(18,9): error TS2352: Conversion of type 'I2' to type 'I3' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 
 
 ==== tests/cases/conformance/types/typeRelationships/comparable/typeAssertionsWithIntersectionTypes01.ts (2 errors) ====
@@ -23,12 +23,12 @@ tests/cases/conformance/types/typeRelationships/comparable/typeAssertionsWithInt
     
     var a = <I1 & I3>z;
             ~~~~~~~~~~
-!!! error TS2352: Type 'I2' cannot be converted to type 'I1 & I3'.
+!!! error TS2352: Conversion of type 'I2' to type 'I1 & I3' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 !!! error TS2352:   Type 'I2' is not comparable to type 'I3'.
 !!! error TS2352:     Property 'p3' is missing in type 'I2'.
     var b = <I3>z;
             ~~~~~
-!!! error TS2352: Type 'I2' cannot be converted to type 'I3'.
+!!! error TS2352: Conversion of type 'I2' to type 'I3' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
     var c = <I2>z;
     var d = <I1>y;
     
\ No newline at end of file
diff --git a/tests/baselines/reference/typeAssertionsWithUnionTypes01.errors.txt b/tests/baselines/reference/typeAssertionsWithUnionTypes01.errors.txt
index 7bc2a9df9b3ad..665b49a05cf38 100644
--- a/tests/baselines/reference/typeAssertionsWithUnionTypes01.errors.txt
+++ b/tests/baselines/reference/typeAssertionsWithUnionTypes01.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/conformance/types/typeRelationships/comparable/typeAssertionsWithUnionTypes01.ts(14,9): error TS2352: Type 'I1' cannot be converted to type 'number'.
+tests/cases/conformance/types/typeRelationships/comparable/typeAssertionsWithUnionTypes01.ts(14,9): error TS2352: Conversion of type 'I1' to type 'number' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
 
 
 ==== tests/cases/conformance/types/typeRelationships/comparable/typeAssertionsWithUnionTypes01.ts (1 errors) ====
@@ -17,7 +17,7 @@ tests/cases/conformance/types/typeRelationships/comparable/typeAssertionsWithUni
     var a = <number | I2>z;
     var b = <number>z;
             ~~~~~~~~~
-!!! error TS2352: Type 'I1' cannot be converted to type 'number'.
+!!! error TS2352: Conversion of type 'I1' to type 'number' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
     var c = <I2>z;
     var d = <I1>y;
     
\ No newline at end of file