[commit: ghc] master: Parse holes as infix operators (6c869f9)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/6c869f906b879bc746ea1aa3e79e02f146d85093/ghc

>---------------------------------------------------------------

commit 6c869f906b879bc746ea1aa3e79e02f146d85093
Author: Ömer Sinan Ağacan <omeragacan at gmail.com>
Date:   Sun Jan 8 07:52:53 2017 +0300

    Parse holes as infix operators
    
    Reported as #13050. Since holes are expressions but not identifiers,
    holes were not allowed in infix operator position. This patch introduces
    a new production in infix operator parser to allow this.
    
    Reviewers: simonpj, austin, bgamari
    
    Reviewed By: simonpj
    
    Subscribers: simonpj, RyanGlScott, thomie, mpickering
    
    Differential Revision: https://phabricator.haskell.org/D2910
    
    GHC Trac Issues: #13050


>---------------------------------------------------------------

6c869f906b879bc746ea1aa3e79e02f146d85093
 compiler/hsSyn/HsExpr.hs                           |  1 +
 compiler/parser/Parser.y                           |  3 +++
 testsuite/tests/typecheck/should_compile/T13050.hs |  6 +++++
 .../tests/typecheck/should_compile/T13050.stderr   | 31 ++++++++++++++++++++++
 testsuite/tests/typecheck/should_compile/all.T     |  1 +
 5 files changed, 42 insertions(+)

diff --git a/compiler/hsSyn/HsExpr.hs b/compiler/hsSyn/HsExpr.hs
index 1b6ccdc..18bf54a 100644
--- a/compiler/hsSyn/HsExpr.hs
+++ b/compiler/hsSyn/HsExpr.hs
@@ -823,6 +823,7 @@ ppr_expr (OpApp e1 op _ e2)
   = case unLoc op of
       HsVar (L _ v) -> pp_infixly v
       HsRecFld f    -> pp_infixly f
+      HsUnboundVar h at TrueExprHole{} -> pp_infixly (unboundVarOcc h)
       _             -> pp_prefixly
   where
     pp_e1 = pprDebugParendExpr e1   -- In debug mode, add parens
diff --git a/compiler/parser/Parser.y b/compiler/parser/Parser.y
index 3fc20a1..dfb6755 100644
--- a/compiler/parser/Parser.y
+++ b/compiler/parser/Parser.y
@@ -3132,6 +3132,9 @@ varop   :: { Located RdrName }
 qop     :: { LHsExpr RdrName }   -- used in sections
         : qvarop                { sL1 $1 $ HsVar $1 }
         | qconop                { sL1 $1 $ HsVar $1 }
+        | '`' '_' '`'           {% ams (sLL $1 $> EWildPat)
+                                       [mj AnnBackquote $1,mj AnnVal $2
+                                       ,mj AnnBackquote $3] }
 
 qopm    :: { LHsExpr RdrName }   -- used in sections
         : qvaropm               { sL1 $1 $ HsVar $1 }
diff --git a/testsuite/tests/typecheck/should_compile/T13050.hs b/testsuite/tests/typecheck/should_compile/T13050.hs
new file mode 100644
index 0000000..d40c476
--- /dev/null
+++ b/testsuite/tests/typecheck/should_compile/T13050.hs
@@ -0,0 +1,6 @@
+module HolesInfix where
+
+f, g, q :: Int -> Int -> Int
+f x y = _ x y
+g x y = x `_` y
+q x y = x `_a` y
diff --git a/testsuite/tests/typecheck/should_compile/T13050.stderr b/testsuite/tests/typecheck/should_compile/T13050.stderr
new file mode 100644
index 0000000..b8ccd76
--- /dev/null
+++ b/testsuite/tests/typecheck/should_compile/T13050.stderr
@@ -0,0 +1,31 @@
+
+T13050.hs:4:9: warning: [-Wtyped-holes (in -Wdefault)]
+    • Found hole: _ :: Int -> Int -> Int
+    • In the expression: _
+      In the expression: _ x y
+      In an equation for ‘f’: f x y = _ x y
+    • Relevant bindings include
+        y :: Int (bound at T13050.hs:4:5)
+        x :: Int (bound at T13050.hs:4:3)
+        f :: Int -> Int -> Int (bound at T13050.hs:4:1)
+
+T13050.hs:5:11: warning: [-Wtyped-holes (in -Wdefault)]
+    • Found hole: _ :: Int -> Int -> Int
+    • In the expression: _
+      In the expression: x `_` y
+      In an equation for ‘g’: g x y = x `_` y
+    • Relevant bindings include
+        y :: Int (bound at T13050.hs:5:5)
+        x :: Int (bound at T13050.hs:5:3)
+        g :: Int -> Int -> Int (bound at T13050.hs:5:1)
+
+T13050.hs:6:11: warning: [-Wtyped-holes (in -Wdefault)]
+    • Found hole: _a :: Int -> Int -> Int
+      Or perhaps ‘_a’ is mis-spelled, or not in scope
+    • In the expression: _a
+      In the expression: x `_a` y
+      In an equation for ‘q’: q x y = x `_a` y
+    • Relevant bindings include
+        y :: Int (bound at T13050.hs:6:5)
+        x :: Int (bound at T13050.hs:6:3)
+        q :: Int -> Int -> Int (bound at T13050.hs:6:1)
diff --git a/testsuite/tests/typecheck/should_compile/all.T b/testsuite/tests/typecheck/should_compile/all.T
index d628366..40d31bb 100644
--- a/testsuite/tests/typecheck/should_compile/all.T
+++ b/testsuite/tests/typecheck/should_compile/all.T
@@ -563,3 +563,4 @@ test('T12911', normal, compile, [''])
 test('T12925', normal, compile, [''])
 test('T12919', expect_broken(12919), compile, [''])
 test('T12936', normal, compile, [''])
+test('T13050', normal, compile, ['-fdefer-type-errors'])