gc: simplify complex typecheck

do not convert to float prematurely.

R=ken2
CC=golang-dev
https://golang.org/cl/311041

src/cmd/gc/const.c

@@ -888,6 +888,9 @@ nodcplxlit(Val r, Val i)
 	Node *n;
 	Mpcplx *c;
 
+	r = toflt(r);
+	i = toflt(i);
+
 	c = mal(sizeof(*c));
 	n = nod(OLITERAL, N, N);
 	n->type = types[TIDEAL];

src/cmd/gc/print.c

@@ -309,6 +309,26 @@ exprfmt(Fmt *f, Node *n, int prec)
 		fmtprint(f, ")");
 		break;
 
+	case OCMPLX:
+		fmtprint(f, "cmplx(");
+		exprfmt(f, n->left, 0);
+		fmtprint(f, ", ");
+		exprfmt(f, n->right, 0);
+		fmtprint(f, ")");
+		break;
+
+	case OREAL:
+		fmtprint(f, "real(");
+		exprfmt(f, n->left, 0);
+		fmtprint(f, ")");
+		break;
+
+	case OIMAG:
+		fmtprint(f, "imag(");
+		exprfmt(f, n->left, 0);
+		fmtprint(f, ")");
+		break;
+
 	case OCONV:
 	case OCONVNOP:
 	case OCONVSLICE:

src/cmd/gc/typecheck.c

@@ -788,51 +788,34 @@ reswitch:
 		if(l->type == T || r->type == T)
 			goto error;
 		defaultlit2(&l, &r, 0);
-		if(l->op == OLITERAL && r->op == OLITERAL) {
-			// make it a complex literal
-			switch(l->type->etype) {
-			default:
-				yyerror("real and imag parts must be the floating");
-				goto error;
-			case TIDEAL:
-				convlit(&l, types[TFLOAT]);
-				convlit(&r, types[TFLOAT]);
-				t = types[TIDEAL];
-				// fallthrough
-			case TFLOAT:
-				t = types[TCOMPLEX];
-				break;
-			case TFLOAT32:
-				t = types[TCOMPLEX64];
-				break;
-			case TFLOAT64:
-				t = types[TCOMPLEX128];
-				break;
-			}
-			n = nodcplxlit(l->val, r->val);
-			n->type = t;
-			goto ret;
-		}
 		n->left = l;
 		n->right = r;
 		if(l->type->etype != l->type->etype) {
-			yyerror("real and imag parts must be the same type");
+		badcmplx:
+			yyerror("invalid operation: %#N (cmplx of types %T, %T)", n, l->type, r->type);
 			goto error;
 		}
 		switch(l->type->etype) {
 		default:
-			yyerror("real and imag parts must be the floating");
-			goto error;
+			goto badcmplx;
+		case TIDEAL:
+			t = types[TIDEAL];
+			break;
 		case TFLOAT:
-			n->type = types[TCOMPLEX];
+			t = types[TCOMPLEX];
 			break;
 		case TFLOAT32:
-			n->type = types[TCOMPLEX64];
+			t = types[TCOMPLEX64];
 			break;
 		case TFLOAT64:
-			n->type = types[TCOMPLEX128];
+			t = types[TCOMPLEX128];
 			break;
 		}
+		if(l->op == OLITERAL && r->op == OLITERAL) {
+			// make it a complex literal
+			n = nodcplxlit(l->val, r->val);
+		}
+		n->type = t;
 		goto ret;
 
 	case OCLOSED: