[wasm] Fix error output for duplicate exports

There are other things to export beside functions. Thus, also print the
export kind when printing an error for duplicate export names.

R=titzer@chromium.org

Change-Id: I7477040dda274a16cfd776d7ac8db6e50a197b97
Reviewed-on: https://chromium-review.googlesource.com/564940Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46503}

src/wasm/module-decoder.cc

@@ -606,8 +606,9 @@ class ModuleDecoder : public Decoder {
         DCHECK(!cmp_less(*it, *last));  // Vector must be sorted.
         if (!cmp_less(*last, *it)) {
           const byte* pc = start() + GetBufferRelativeOffset(it->name.offset());
-          errorf(pc, "Duplicate export name '%.*s' for functions %d and %d",
-                 it->name.length(), pc, last->index, it->index);
+          errorf(pc, "Duplicate export name '%.*s' for %s %d and %s %d",
+                 it->name.length(), pc, ExternalKindName(last->kind),
+                 last->index, ExternalKindName(it->kind), it->index);
           break;
         }
       }

src/wasm/wasm-module.cc

@@ -1127,3 +1127,17 @@ Handle<Code> LazyCompilationOrchestrator::CompileLazy(
   DCHECK_EQ(Code::WASM_FUNCTION, ret->kind());
   return handle(ret, isolate);
 }
+
+const char* wasm::ExternalKindName(WasmExternalKind kind) {
+  switch (kind) {
+    case kExternalFunction:
+      return "function";
+    case kExternalTable:
+      return "table";
+    case kExternalMemory:
+      return "memory";
+    case kExternalGlobal:
+      return "global";
+  }
+  return "unknown";
+}

src/wasm/wasm-module.h

@@ -512,6 +512,8 @@ class LazyCompilationOrchestrator {
                            int exported_func_index, bool patch_caller);
 };
 
+const char* ExternalKindName(WasmExternalKind);
+
 namespace testing {
 void ValidateInstancesChain(Isolate* isolate,
                             Handle<WasmModuleObject> module_obj,

test/mjsunit/wasm/export-global.js

@@ -38,3 +38,21 @@ load("test/mjsunit/wasm/wasm-module-builder.js");
   builder.addGlobal(kWasmI64, false).exportAs('g');
   assertThrows(() => builder.instantiate(), WebAssembly.LinkError);
 })();
+
+(function duplicateGlobalExportName() {
+  var builder = new WasmModuleBuilder();
+  builder.addGlobal(kWasmI64, false).exportAs('g');
+  builder.addGlobal(kWasmI64, false).exportAs('g');
+  assertThrows(
+      () => builder.instantiate(), WebAssembly.CompileError,
+      /Duplicate export name 'g' for global 0 and global 1/);
+})();
+
+(function exportNameClashWithFunction() {
+  var builder = new WasmModuleBuilder();
+  builder.addGlobal(kWasmI64, false).exportAs('foo');
+  builder.addFunction('f', kSig_v_v).addBody([]).exportAs('foo');
+  assertThrows(
+      () => builder.instantiate(), WebAssembly.CompileError,
+      /Duplicate export name 'foo' for global 0 and function 0/);
+})();

test/mjsunit/wasm/export-table.js

@@ -106,12 +106,8 @@ load("test/mjsunit/wasm/wasm-module-builder.js");
   builder.addFunction("two",   kSig_v_v).addBody([kExprNop]).exportAs("other");
   builder.addFunction("three", kSig_v_v).addBody([kExprNop]).exportAs("main");
 
-  try {
-    builder.instantiate();
-    assertUnreachable("should have thrown an exception");
-  } catch (e) {
-    assertContains("Duplicate export", e.toString());
-  }
+  assertThrows(() => builder.instantiate(), WebAssembly.CompileError,
+    /Duplicate export name 'main' for function 0 and function 2/);
 })();