better error messages: use <T1, T2> instead of (T1, T2) in order to prevent confusions with tuple types

compiler/msgs.nim

@@ -272,7 +272,7 @@ const
     errXStackEscape: "address of '$1' may not escape its stack frame",
     errVarForOutParamNeededX: "for a \'var\' type a variable needs to be passed; but '$1' is immutable",
     errPureTypeMismatch: "type mismatch",
-    errTypeMismatch: "type mismatch: got (",
+    errTypeMismatch: "type mismatch: got <",
     errButExpected: "but expected one of: ",
     errButExpectedX: "but expected \'$1\'",
     errAmbiguousCallXYZ: "ambiguous call; both $1 and $2 match for: $3",

compiler/semcall.nim

@@ -156,14 +156,14 @@ proc presentFailedCandidates(c: PContext, n: PNode, errors: CandidateErrors):
       add(candidates, err.sym.getProcHeader(prefer))
     add(candidates, "\n")
     if err.firstMismatch != 0 and n.len > 2:
-      add(candidates, "first type mismatch at position: " & $err.firstMismatch &
-        "\nrequired type: ")
+      add(candidates, "  first type mismatch at position: " & $err.firstMismatch &
+        "\n  required type: ")
       if err.firstMismatch < err.sym.typ.len:
         candidates.add typeToString(err.sym.typ.sons[err.firstMismatch])
       else:
         candidates.add "none"
       if err.firstMismatch < n.len:
-        candidates.add "\nbut expression '"
+        candidates.add "\n  but expression '"
         candidates.add renderTree(n[err.firstMismatch])
         candidates.add "' is of type: "
         candidates.add typeToString(n[err.firstMismatch].typ)
@@ -190,7 +190,7 @@ proc notFoundError*(c: PContext, n: PNode, errors: CandidateErrors) =
   let (prefer, candidates) = presentFailedCandidates(c, n, errors)
   var result = msgKindToString(errTypeMismatch)
   add(result, describeArgs(c, n, 1, prefer))
-  add(result, ')')
+  add(result, '>')
   if candidates != "":
     add(result, "\n" & msgKindToString(errButExpected) & "\n" & candidates)
   localError(n.info, errGenerated, result & "\nexpression: " & $n)

compiler/semexprs.nim

@@ -735,7 +735,7 @@ proc semIndirectOp(c: PContext, n: PNode, flags: TExprFlags): PNode =
             hasErrorType = true
             break
         if not hasErrorType:
-          add(msg, ")\n" & msgKindToString(errButExpected) & "\n" &
+          add(msg, ">\n" & msgKindToString(errButExpected) & "\n" &
               typeToString(n.sons[0].typ))
           localError(n.info, errGenerated, msg)
         return errorNode(c, n)

compiler/semtypes.nim

@@ -1149,8 +1149,8 @@ proc semGeneric(c: PContext, n: PNode, s: PSym, prev: PType): PType =
 
     if m.state != csMatch:
       let err = "cannot instantiate " & typeToString(t) & "\n" &
-                "got: (" & describeArgs(c, n) & ")\n" &
-                "but expected: (" & describeArgs(c, t.n, 0) & ")"
+                "got: <" & describeArgs(c, n) & ">\n" &
+                "but expected: <" & describeArgs(c, t.n, 0) & ">"
       localError(n.info, errGenerated, err)
       return newOrPrevType(tyError, prev, c)
 

compiler/types.nim

@@ -1620,7 +1620,7 @@ proc typeMismatch*(info: TLineInfo, formal, actual: PType) =
     let desc = typeToString(formal, preferDesc)
     let x = if named == desc: named else: named & " = " & desc
     var msg = msgKindToString(errTypeMismatch) &
-              typeToString(actual) & ") " &
+              typeToString(actual) & "> " &
               msgKindToString(errButExpectedX) % [x]
 
     if formal.kind == tyProc and actual.kind == tyProc: