Colours are nice

compiler/semcall.nim

@@ -11,6 +11,8 @@
 # included from sem.nim
 
 from algorithm import sort
+import sets
+from terminal import ForegroundColor
 
 proc sameMethodDispatcher(a, b: PSym): bool =
   result = false
@@ -160,6 +162,8 @@ proc renderNotLValue(n: PNode): string =
   elif n.kind in {nkHiddenStdConv, nkHiddenSubConv} and n.len == 2:
     result = typeToString(n.typ.skipTypes(abstractVar)) & "(" & result & ")"
 
+proc color(str: string, color: ForegroundColor): string = "\x1b[" & $(color.ord) & "m" & str & "\x1b[0m"
+
 proc presentFailedCandidates(c: PContext, n: PNode, errors: CandidateErrors):
                             (TPreferedDesc, string) =
   var prefer = preferName
@@ -198,6 +202,7 @@ proc presentFailedCandidates(c: PContext, n: PNode, errors: CandidateErrors):
   var candidatesAll: seq[string]
   var candidates = ""
   var skipped = 0
+  var immutSyms: HashSet[string] #All failed immutable params
   for err in errors:
     candidates.setLen 0
     if filterOnlyFirst and err.firstMismatch.arg == 1:
@@ -208,23 +213,24 @@ proc presentFailedCandidates(c: PContext, n: PNode, errors: CandidateErrors):
             {renderNoBody, renderNoComments, renderNoPragmas}))
     else:
       candidates.add(getProcHeader(c.config, err.sym, prefer))
+    let immutMsgIndex = candidates.len
     candidates.addDeclaredLocMaybe(c.config, err.sym)
     candidates.add("\n")
     let nArg = if err.firstMismatch.arg < n.len: n[err.firstMismatch.arg] else: nil
     let nameParam = if err.firstMismatch.formal != nil: err.firstMismatch.formal.name.s else: ""
     if n.len > 1:
-      candidates.add("  first type mismatch at position: " & $err.firstMismatch.arg)
+      candidates.add(("  first type mismatch at position: " & $err.firstMismatch.arg).color(fgRed))
       # candidates.add "\n  reason: " & $err.firstMismatch.kind # for debugging
       case err.firstMismatch.kind
       of kUnknownNamedParam:
         if nArg == nil:
-          candidates.add("\n  unknown named parameter")
+          candidates.add("\n  unknown named parameter".color(fgRed))
         else:
-          candidates.add("\n  unknown named parameter: " & $nArg[0])
-      of kAlreadyGiven: candidates.add("\n  named param already provided: " & $nArg[0])
-      of kPositionalAlreadyGiven: candidates.add("\n  positional param was already given as named param")
-      of kExtraArg: candidates.add("\n  extra argument given")
-      of kMissingParam: candidates.add("\n  missing parameter: " & nameParam)
+          candidates.add(("\n  unknown named parameter: " & $nArg[0]).color(fgRed))
+      of kAlreadyGiven: candidates.add(("\n  named param already provided: " & $nArg[0]).color(fgRed))
+      of kPositionalAlreadyGiven: candidates.add("\n  positional param was already given as named param".color(fgRed))
+      of kExtraArg: candidates.add("\n  extra argument given".color(fgRed))
+      of kMissingParam: candidates.add(("\n  missing parameter: " & nameParam).color(fgRed))
       of kTypeMismatch, kVarNeeded:
         doAssert nArg != nil
         var wanted = err.firstMismatch.formal.typ
@@ -234,25 +240,34 @@ proc presentFailedCandidates(c: PContext, n: PNode, errors: CandidateErrors):
         candidates.addDeclaredLocMaybe(c.config, wanted)
         candidates.add "\n  but expression '"
         if err.firstMismatch.kind == kVarNeeded:
-          candidates.add renderNotLValue(nArg)
-          candidates.add "' is immutable, not 'var'"
+          candidates.add (renderNotLValue(nArg)).color(fgYellow)
+          immutSyms.incl renderNotLValue(nArg)
+          candidates.add "'" & " is immutable, not 'var'".color(fgRed)
         else:
-          candidates.add renderTree(nArg)
-          candidates.add "' is of type: "
+          candidates.add renderTree(nArg).color(fgRed)
+          candidates.add "'" & " is of type: ".color(fgRed)
           var got = nArg.typ
-          candidates.add typeToString(got)
+          candidates.add typeToString(got).color(fgRed)
           candidates.addDeclaredLocMaybe(c.config, got)
           doAssert wanted != nil
           if got != nil: effectProblem(wanted, got, candidates, c)
       of kUnknown: discard "do not break 'nim check'"
-      candidates.add "\n"
+      candidates.add "\n\n"
       if err.firstMismatch.arg == 1 and nArg.kind == nkTupleConstr and
           n.kind == nkCommand:
         maybeWrongSpace = true
     for diag in err.diagnostics:
       candidates.add(diag & "\n")
     candidatesAll.add candidates
   candidatesAll.sort # fix #13538
+  if immutSyms.len > 0:
+    let wrappedSyms = block:
+      var res = ""
+      for sym in immutSyms:
+        if res.len > 0: res.add(", ")
+        res.add("`" & sym & "`")
+      res
+    candidatesAll.insert(("\nAtleast one of the mismatches is due to " & wrappedSyms & " being immutable.\n\n").color(fgYellow), 0)
   candidates = join(candidatesAll)
   if skipped > 0:
     candidates.add($skipped & " other mismatching symbols have been " &
@@ -265,10 +280,10 @@ proc presentFailedCandidates(c: PContext, n: PNode, errors: CandidateErrors):
 const
   errTypeMismatch = "type mismatch: got <"
   errButExpected = "but expected one of: "
-  errUndeclaredField = "undeclared field: '$1'"
-  errUndeclaredRoutine = "attempting to call undeclared routine: '$1'"
-  errBadRoutine = "attempting to call routine: '$1'$2"
-  errAmbiguousCallXYZ = "ambiguous call; both $1 and $2 match for: $3"
+  errUndeclaredField = "undeclared field: '$1'".color(fgRed)
+  errUndeclaredRoutine = "attempting to call undeclared routine: '$1'".color(fgRed)
+  errBadRoutine = "attempting to call routine: '$1'$2".color(fgRed)
+  errAmbiguousCallXYZ = "ambiguous call; both $1 and $2 match for: $3".color(fgRed)
 
 proc notFoundError*(c: PContext, n: PNode, errors: CandidateErrors) =
   # Gives a detailed error message; this is separated from semOverloadedCall,