Implement basic support for importing source locations from one AST
into another AST, including their include history. Here's an example
error that involves a conflict merging a variable with different types
in two translation units (diagnosed in the third AST context into
which everything is merged).

/Volumes/Data/dgregor/Projects/llvm/tools/clang/test/ASTMerge/Inputs/var2.c:3:5:
error: external variable 'x2' declared with incompatible types in
different translation units ('int' vs. 'double')
int x2;
    ^
In file included from
/Volumes/Data/dgregor/Projects/llvm/tools/clang/test/ASTMerge/Inputs/var1.c:3:
/Volumes/Data/dgregor/Projects/llvm/tools/clang/test/ASTMerge/Inputs/var1.h:1:8:
note: declared here with type 'double'
double x2;
       ^

Although we maintain include history, we do not maintain macro
instantiation history across a merge. Instead, we map down to the
spelling location (for now!).



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@95732 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/ASTMerge/Inputs/var1.c b/test/ASTMerge/Inputs/var1.c
index c87e58b..4652589 100644
--- a/test/ASTMerge/Inputs/var1.c
+++ b/test/ASTMerge/Inputs/var1.c
@@ -1,2 +1,3 @@
 int *x0;
 float **x1;
+#include "var1.h"
diff --git a/test/ASTMerge/Inputs/var2.c b/test/ASTMerge/Inputs/var2.c
index 526a45b..e93a010 100644
--- a/test/ASTMerge/Inputs/var2.c
+++ b/test/ASTMerge/Inputs/var2.c
@@ -1,2 +1,3 @@
 int *x0;
 double *x1;
+int x2;
diff --git a/test/ASTMerge/var.c b/test/ASTMerge/var.c
index 4fda4ac..98ad7ab 100644
--- a/test/ASTMerge/var.c
+++ b/test/ASTMerge/var.c
@@ -2,4 +2,8 @@
 // RUN: %clang_cc1 -emit-pch -o %t.2.ast %S/Inputs/var2.c
 // RUN: %clang_cc1 -ast-merge %t.1.ast -ast-merge %t.2.ast -fsyntax-only %s 2>&1 | FileCheck %s
 
-// CHECK: error: external variable 'x1' declared with incompatible types in different translation units ('double *' vs. 'float **')
+// CHECK: var2.c:2:9: error: external variable 'x1' declared with incompatible types in different translation units ('double *' vs. 'float **')
+// CHECK: var1.c:2:9: note: declared here with type 'float **'
+// CHECK: var2.c:3:5: error: external variable 'x2' declared with incompatible types in different translation units ('int' vs. 'double')
+// CHECK: In file included from{{.*}}var1.c:3:
+// CHECK: var1.h:1:8: note: declared here with type 'double'