Go patch committed: Always use int context for index values

[Ian Lance Taylor via Gcc-patches]

This patch changes the Go frontend to always use a context that
expects an int type when determining the type of an index value.  This
is for https://golang.org/issue/14844.  This requires updating one of
the tests in the testsuite to the source version.  Bootstrapped and
ran Go testsuite on x86_64-pc-linux-gnu.  Committed to mainline.

Ian

8d8fea8a57068a0c5f0c1df766679a25f4272481
diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index af4d0526b2f..698969fc8c8 100644
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-68b1c7659a6b25d537a4ff3365ab070fa6215b0b
+af683486b4de5503b2b6d9ae974a2ab1eeb92290
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
diff --git a/gcc/go/gofrontend/expressions.cc b/gcc/go/gofrontend/expressions.cc
index dc7399ebb3a..d1546300d0e 100644
--- a/gcc/go/gofrontend/expressions.cc
+++ b/gcc/go/gofrontend/expressions.cc
@@ -12802,24 +12802,11 @@ Array_index_expression::do_determine_type(const 
Type_context*)
   this->array_->determine_type_no_context();
 
   Type_context index_context(Type::lookup_integer_type("int"), false);
-  if (this->start_->is_constant())
-    this->start_->determine_type(&index_context);
-  else
-    this->start_->determine_type_no_context();
+  this->start_->determine_type(&index_context);
   if (this->end_ != NULL)
-    {
-      if (this->end_->is_constant())
-        this->end_->determine_type(&index_context);
-      else
-        this->end_->determine_type_no_context();
-    }
+    this->end_->determine_type(&index_context);
   if (this->cap_ != NULL)
-    {
-      if (this->cap_->is_constant())
-        this->cap_->determine_type(&index_context);
-      else
-        this->cap_->determine_type_no_context();
-    }
+    this->cap_->determine_type(&index_context);
 }
 
 // Check types of an array index.
@@ -13488,17 +13475,9 @@ String_index_expression::do_determine_type(const 
Type_context*)
   this->string_->determine_type_no_context();
 
   Type_context index_context(Type::lookup_integer_type("int"), false);
-  if (this->start_->is_constant())
-    this->start_->determine_type(&index_context);
-  else
-    this->start_->determine_type_no_context();
+  this->start_->determine_type(&index_context);
   if (this->end_ != NULL)
-    {
-      if (this->end_->is_constant())
-        this->end_->determine_type(&index_context);
-      else
-        this->end_->determine_type_no_context();
-    }
+    this->end_->determine_type(&index_context);
 }
 
 // Check types of a string index.
diff --git a/gcc/testsuite/go.test/test/shift1.go 
b/gcc/testsuite/go.test/test/shift1.go
index 04f5321b73f..d6a6c38839f 100644
--- a/gcc/testsuite/go.test/test/shift1.go
+++ b/gcc/testsuite/go.test/test/shift1.go
@@ -1,6 +1,6 @@
 // errorcheck
 
-// Copyright 2011 The Go Authors.  All rights reserved.
+// Copyright 2011 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
@@ -18,13 +18,13 @@ func h(x float64) int     { return 0 }
 var (
        s uint    = 33
        u         = 1.0 << s // ERROR "invalid operation|shift of non-integer 
operand"
-       v float32 = 1 << s   // ERROR "invalid" "as type float32"
+       v float32 = 1 << s   // ERROR "invalid"
 )
 
 // non-constant shift expressions
 var (
-       e1       = g(2.0 << s) // ERROR "invalid|shift of non-integer operand" 
"as type interface"
-       f1       = h(2 << s)   // ERROR "invalid" "as type float64"
+       e1       = g(2.0 << s) // ERROR "invalid|shift of non-integer operand"
+       f1       = h(2 << s)   // ERROR "invalid"
        g1 int64 = 1.1 << s    // ERROR "truncated"
 )
 
@@ -66,8 +66,15 @@ func _() {
                u2         = 1<<s != 1.0 // ERROR "non-integer|float64"
                v  float32 = 1 << s      // ERROR "non-integer|float32"
                w  int64   = 1.0 << 33   // 1.0<<33 is a constant shift 
expression
+
                _, _, _, _, _, _, _, _, _, _ = j, k, m, n, o, u, u1, u2, v, w
        )
+
+       // non constants arguments trigger a different path
+       f2 := 1.2
+       s2 := "hi"
+       _ = f2 << 2 // ERROR "shift of type float64|non-integer"
+       _ = s2 << 2 // ERROR "shift of type string|non-integer"
 }
 
 // shifts in comparisons w/ untyped operands
@@ -146,8 +153,7 @@ func _() {
        var a []int
        _ = a[1<<s]
        _ = a[1.]
-       // For now, the spec disallows these. We may revisit past Go 1.1.
-       _ = a[1.<<s]  // ERROR "integer|shift of type float64"
+       _ = a[1.<<s]
        _ = a[1.1<<s] // ERROR "integer|shift of type float64"
 
        _ = make([]int, 1)