Treat (=) as a special function name.

Includes a regression test.

Fixes #884

src/Idris/ParseOps.hs

@@ -82,12 +82,16 @@ backtick = Infix (do indentPropHolds gtProp
  optional namespace
 
 @
-  OperatorFront ::= (Identifier_t '.')? '(' Operator_t ')';
+  OperatorFront ::=
+    '(' '=' ')'
+    | (Identifier_t '.')? '(' Operator_t ')'
+    ;
 @
 
 -}
 operatorFront :: IdrisParser Name
-operatorFront = maybeWithNS (lchar '(' *> operator <* lchar ')') False []
+operatorFront = try ((lchar '(' *> reservedOp "="  <* lchar ')') >> (return eqTy))
+            <|> maybeWithNS (lchar '(' *> operator <* lchar ')') False []
 
 {- | Parses a function (either normal name or operator)
 

test/reg037/reg037.idr

@@ -0,0 +1,9 @@
+
+--- Parser regression for (=) as a function name (fnName)
+
+class Foo (t : (A : Type) -> (B : Type) -> A -> B -> Type) where
+  foo : (A : Type) -> (B : Type) -> (x : A) -> (y : B) -> t A B x y -> t A B x y
+
+instance Foo (=) where
+  foo A B x y prf = prf
+

test/reg037/run

@@ -0,0 +1,3 @@
+#!/usr/bin/env bash
+idris --check reg037.idr
+rm -f reg037 *.ibc