resolver: Error when calling shadowed functions

The fix involves unifying the dependency logic of DependencyScanner, which also cleans up the code quite a bit.

Also:
* Correctly resolve parameter type before declaring the parameter variable.
* Fix bonkers typos in utils::Lookup.

Fixed: tint:1442
Change-Id: I77b548e148b461f87ec10e8272c398f6fee297bd
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/81102
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: James Price <jrprice@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>

src/resolver/call_validation_test.cc

@@ -265,6 +265,24 @@ TEST_F(ResolverCallValidationTest, CallVariable) {
 note: 'v' declared here)");
 }
 
+TEST_F(ResolverCallValidationTest, CallVariableShadowsFunction) {
+  // fn x() {}
+  // fn f() {
+  //   var x : i32;
+  //   x();
+  // }
+  Func("x", {}, ty.void_(), {});
+  Func("f", {}, ty.void_(),
+       {
+           Decl(Var(Source{{56, 78}}, "x", ty.i32())),
+           CallStmt(Call(Source{{12, 34}}, "x")),
+       });
+
+  EXPECT_FALSE(r()->Resolve());
+  EXPECT_EQ(r()->error(), R"(error: cannot call variable 'x'
+56:78 note: 'x' declared here)");
+}
+
 }  // namespace
 }  // namespace resolver
 }  // namespace tint

src/resolver/dependency_graph.cc

@@ -173,6 +173,16 @@ class DependencyScanner {
   /// Traverses the function, performing symbol resolution and determining
   /// global dependencies.
   void TraverseFunction(const ast::Function* func) {
+    // Perform symbol resolution on all the parameter types before registering
+    // the parameters themselves. This allows the case of declaring a parameter
+    // with the same identifier as its type.
+    for (auto* param : func->params) {
+      TraverseType(param->type);
+    }
+    // Resolve the return type
+    TraverseType(func->return_type);
+
+    // Push the scope stack for the parameters and function body.
     scope_stack_.Push();
     TINT_DEFER(scope_stack_.Pop());
 
@@ -181,12 +191,10 @@ class DependencyScanner {
         graph_.shadows.emplace(param, shadows);
       }
       Declare(param->symbol, param);
-      TraverseType(param->type);
     }
     if (func->body) {
       TraverseStatements(func->body->statements);
     }
-    TraverseType(func->return_type);
   }
 
   /// Traverses the statements, performing symbol resolution and determining
@@ -295,38 +303,15 @@ class DependencyScanner {
     ast::TraverseExpressions(
         root, diagnostics_, [&](const ast::Expression* expr) {
           if (auto* ident = expr->As<ast::IdentifierExpression>()) {
-            auto* node = scope_stack_.Get(ident->symbol);
-            if (node == nullptr) {
-              if (!IsBuiltin(ident->symbol)) {
-                UnknownSymbol(ident->symbol, ident->source, "identifier");
-              }
-              return ast::TraverseAction::Descend;
-            }
-            auto global_it = globals_.find(ident->symbol);
-            if (global_it != globals_.end() &&
-                node == global_it->second->node) {
-              AddGlobalDependency(ident, ident->symbol, "identifier",
-                                  "references");
-            } else {
-              graph_.resolved_symbols.emplace(ident, node);
-            }
+            AddDependency(ident, ident->symbol, "identifier", "references");
           }
           if (auto* call = expr->As<ast::CallExpression>()) {
             if (call->target.name) {
-              if (!IsBuiltin(call->target.name->symbol)) {
-                AddGlobalDependency(call->target.name,
-                                    call->target.name->symbol, "function",
-                                    "calls");
-                graph_.resolved_symbols.emplace(
-                    call,
-                    utils::Lookup(graph_.resolved_symbols, call->target.name));
-              }
+              AddDependency(call->target.name, call->target.name->symbol,
+                            "function", "calls");
             }
             if (call->target.type) {
               TraverseType(call->target.type);
-              graph_.resolved_symbols.emplace(
-                  call,
-                  utils::Lookup(graph_.resolved_symbols, call->target.type));
             }
           }
           if (auto* cast = expr->As<ast::BitcastExpression>()) {
@@ -360,7 +345,7 @@ class DependencyScanner {
       return;
     }
     if (auto* tn = ty->As<ast::TypeName>()) {
-      AddGlobalDependency(tn, tn->name, "type", "references");
+      AddDependency(tn, tn->name, "type", "references");
       return;
     }
     if (auto* vec = ty->As<ast::Vector>()) {
@@ -416,24 +401,31 @@ class DependencyScanner {
     UnhandledNode(diagnostics_, attr);
   }
 
-  /// Adds the dependency to the currently processed global
-  void AddGlobalDependency(const ast::Node* from,
-                           Symbol to,
-                           const char* use,
-                           const char* action) {
-    auto global_it = globals_.find(to);
-    if (global_it != globals_.end()) {
-      auto* global = global_it->second;
+  /// Adds the dependency from `from` to `to`, erroring if `to` cannot be
+  /// resolved.
+  void AddDependency(const ast::Node* from,
+                     Symbol to,
+                     const char* use,
+                     const char* action) {
+    auto* resolved = scope_stack_.Get(to);
+    if (!resolved) {
+      if (!IsBuiltin(to)) {
+        UnknownSymbol(to, from->source, use);
+        return;
+      }
+    }
+
+    if (auto* global = utils::Lookup(globals_, to);
+        global && global->node == resolved) {
       if (dependency_edges_
               .emplace(DependencyEdge{current_global_, global},
                        DependencyInfo{from->source, action})
               .second) {
         current_global_->deps.emplace_back(global);
       }
-      graph_.resolved_symbols.emplace(from, global->node);
-    } else {
-      UnknownSymbol(to, from->source, use);
     }
+
+    graph_.resolved_symbols.emplace(from, resolved);
   }
 
   /// @returns true if `name` is the name of a builtin function

src/resolver/dependency_graph_test.cc

@@ -993,9 +993,9 @@ TEST_F(ResolverDependencyGraphCyclicRefTest, Mixed_RecursiveDependencies) {
 
   EXPECT_FALSE(r()->Resolve());
   EXPECT_EQ(r()->error(),
-            R"(3:1 error: cyclic dependency found: 'S' -> 'A' -> 'S'
-3:10 note: struct 'S' references alias 'A' here
+            R"(2:1 error: cyclic dependency found: 'A' -> 'S' -> 'A'
 2:10 note: alias 'A' references struct 'S' here
+3:10 note: struct 'S' references alias 'A' here
 4:1 error: cyclic dependency found: 'Z' -> 'L' -> 'Z'
 4:10 note: var 'Z' references let 'L' here
 5:10 note: let 'L' references var 'Z' here)");

src/resolver/resolver.cc

@@ -268,8 +268,9 @@ sem::Type* Resolver::Type(const ast::Type* ty) {
         return builder_->create<sem::ExternalTexture>();
       },
       [&](Default) -> sem::Type* {
+        auto* resolved = ResolvedSymbol(ty);
         return Switch(
-            ResolvedSymbol(ty),  //
+            resolved,  //
             [&](sem::Type* type) { return type; },
             [&](sem::Variable* var) {
               auto name =
@@ -291,7 +292,10 @@ sem::Type* Resolver::Type(const ast::Type* ty) {
             },
             [&](Default) {
               TINT_UNREACHABLE(Resolver, diagnostics_)
-                  << "Unhandled ast::Type: " << ty->TypeInfo().name;
+                  << "Unhandled resolved type '"
+                  << (resolved ? resolved->TypeInfo().name : "<null>")
+                  << "' resolved from ast::Type '" << ty->TypeInfo().name
+                  << "'";
               return nullptr;
             });
       });

src/utils/map.h

@@ -29,9 +29,9 @@ namespace utils {
 /// @return the map item value, or `if_missing` if the map does not contain the
 /// given key
 template <typename K, typename V, typename H, typename C, typename KV = K>
-V Lookup(std::unordered_map<K, V, H, C>& map,
+V Lookup(const std::unordered_map<K, V, H, C>& map,
          const KV& key,
-         const KV& if_missing = {}) {
+         const V& if_missing = {}) {
   auto it = map.find(key);
   return it != map.end() ? it->second : if_missing;
 }