diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index ecb8a3a928e..79efc447aa0 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 a9118945b05..1fa89c9d45f 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 61463e5557b..ce9d0313825 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 92603c25cb0..711c320ff7a 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 9431d6123e2..77ebe06fbf9 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 4f957791a24..c634a4a7887 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 344f403906d..c7b00e2a0ca 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 9081480f4ba..5c399faeb62 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 418d435e7fe..afa94b8e333 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 d46963caeed..805f25d8dbc 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 173683297f9..879789e4b23 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 aa5f14f5da8..b4c7a165a91 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 756690f1783..df3093cbc8a 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 401834930f3..4c23bd6d458 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 45f76073363..e01b90d72a5 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 1bda683b88a..ef65803a47d 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 c62c7868e10..89a1724ea9a 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 e5fbfbdbee8..5b7ca138339 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 8cbe096de35..a84d31a341b 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 2024066d9f2..18ac3c27141 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 769353b9965..3f30b649c96 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 6dae5c5d76f..cb664d9a8b9 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 2342065605b..983548016e8 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 c03b08bd0ac..8cb9e8203e7 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 cefc15b8e23..ad6065b0755 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 42ed640e8fc..16a2a726915 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 7bc2a9df9b3..665b49a05cf 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