Move Switch validation from Validator to Resolver

* Formerly, we reported the same error message if we detected no default
clause or more than one. I made it so that we output a different error
message for each. This makes it more clear, and in the case of more than
one, the error source location points at the second default clause,
rather than at the switch statement.

* Add functions to ProgramBuilder to more easily define switch and case
statements.

* Fix broken tests as a result of this change.

Bug: tint:642
Change-Id: Iab4e610a563165862d9bc190772d32a4dd24ac45
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/45880
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>

src/resolver/control_block_validation_test.cc

@@ -0,0 +1,349 @@
+// Copyright 2021 The Tint Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "src/ast/fallthrough_statement.h"
+#include "src/ast/switch_statement.h"
+#include "src/resolver/resolver_test_helper.h"
+
+namespace tint {
+namespace {
+
+class ResolverControlBlockValidationTest : public resolver::TestHelper,
+                                           public testing::Test {};
+
+TEST_F(ResolverControlBlockValidationTest,
+       SwitchSelectorExpressionNoneIntegerType_Fail) {
+  // var a : f32 = 3.14;
+  // switch (a) {
+  //   default: {}
+  // }
+  auto* var = Var("a", ty.f32(), ast::StorageClass::kNone, Expr(3.14f));
+
+  ast::CaseStatementList body;
+  auto* block_default = create<ast::BlockStatement>(ast::StatementList{});
+  body.push_back(
+      create<ast::CaseStatement>(ast::CaseSelectorList{}, block_default));
+
+  auto* block = create<ast::BlockStatement>(ast::StatementList{
+      create<ast::VariableDeclStatement>(var),
+      create<ast::SwitchStatement>(Expr(Source{Source::Location{12, 34}}, "a"),
+                                   body),
+  });
+
+  WrapInFunction(block);
+
+  EXPECT_FALSE(r()->Resolve());
+  EXPECT_EQ(r()->error(),
+            "12:34 error v-0025: switch statement selector expression must be "
+            "of a scalar integer type");
+}
+
+TEST_F(ResolverControlBlockValidationTest, SwitchWithoutDefault_Fail) {
+  // var a : i32 = 2;
+  // switch (a) {
+  //   case 1: {}
+  // }
+  auto* var = Var("a", ty.i32(), ast::StorageClass::kNone, Expr(2));
+
+  ast::CaseSelectorList csl;
+  csl.push_back(Literal(1));
+
+  ast::CaseStatementList body;
+  body.push_back(create<ast::CaseStatement>(
+      csl, create<ast::BlockStatement>(ast::StatementList{})));
+
+  auto* block = create<ast::BlockStatement>(ast::StatementList{
+      create<ast::VariableDeclStatement>(var),
+      create<ast::SwitchStatement>(Source{Source::Location{12, 34}}, Expr("a"),
+                                   body),
+  });
+
+  WrapInFunction(block);
+
+  EXPECT_FALSE(r()->Resolve());
+  EXPECT_EQ(r()->error(),
+            "12:34 error: switch statement must have a default clause");
+}
+
+TEST_F(ResolverControlBlockValidationTest, SwitchWithTwoDefault_Fail) {
+  // var a : i32 = 2;
+  // switch (a) {
+  //   default: {}
+  //   case 1: {}
+  //   default: {}
+  // }
+  auto* var = Var("a", ty.i32(), ast::StorageClass::kNone, Expr(2));
+
+  ast::CaseStatementList switch_body;
+  ast::CaseSelectorList default_csl_1;
+  auto* block_default_1 = create<ast::BlockStatement>(ast::StatementList{});
+  switch_body.push_back(
+      create<ast::CaseStatement>(default_csl_1, block_default_1));
+
+  ast::CaseSelectorList csl_case_1;
+  csl_case_1.push_back(Literal(1));
+  auto* block_case_1 = create<ast::BlockStatement>(ast::StatementList{});
+  switch_body.push_back(create<ast::CaseStatement>(csl_case_1, block_case_1));
+
+  ast::CaseSelectorList default_csl_2;
+  auto* block_default_2 = create<ast::BlockStatement>(ast::StatementList{});
+  switch_body.push_back(create<ast::CaseStatement>(
+      Source{Source::Location{12, 34}}, default_csl_2, block_default_2));
+
+  auto* block = create<ast::BlockStatement>(ast::StatementList{
+      create<ast::VariableDeclStatement>(var),
+      create<ast::SwitchStatement>(Expr("a"), switch_body),
+  });
+
+  WrapInFunction(block);
+
+  EXPECT_FALSE(r()->Resolve());
+  EXPECT_EQ(
+      r()->error(),
+      "12:34 error v-0008: switch statement must have exactly one default "
+      "clause");
+}
+
+TEST_F(ResolverControlBlockValidationTest,
+       SwitchConditionTypeMustMatchSelectorType2_Fail) {
+  // var a : u32 = 2;
+  // switch (a) {
+  //   case 1: {}
+  //   default: {}
+  // }
+  auto* var = Var("a", ty.i32(), ast::StorageClass::kNone, Expr(2));
+
+  ast::CaseStatementList switch_body;
+  ast::CaseSelectorList csl;
+  csl.push_back(create<ast::UintLiteral>(ty.u32(), 1));
+  switch_body.push_back(create<ast::CaseStatement>(
+      Source{Source::Location{12, 34}}, csl,
+      create<ast::BlockStatement>(ast::StatementList{})));
+
+  ast::CaseSelectorList default_csl;
+  auto* block_default = create<ast::BlockStatement>(ast::StatementList{});
+  switch_body.push_back(create<ast::CaseStatement>(default_csl, block_default));
+
+  auto* block = create<ast::BlockStatement>(ast::StatementList{
+      create<ast::VariableDeclStatement>(var),
+      create<ast::SwitchStatement>(Expr("a"), switch_body),
+  });
+  WrapInFunction(block);
+
+  EXPECT_FALSE(r()->Resolve());
+  EXPECT_EQ(r()->error(),
+            "12:34 error v-0026: the case selector values must have the same "
+            "type as the selector expression.");
+}
+
+TEST_F(ResolverControlBlockValidationTest,
+       SwitchConditionTypeMustMatchSelectorType_Fail) {
+  // var a : u32 = 2;
+  // switch (a) {
+  //   case -1: {}
+  //   default: {}
+  // }
+  auto* var = Var("a", ty.u32(), ast::StorageClass::kNone, Expr(2u));
+
+  ast::CaseStatementList switch_body;
+  ast::CaseSelectorList csl;
+  csl.push_back(Literal(-1));
+  switch_body.push_back(create<ast::CaseStatement>(
+      Source{Source::Location{12, 34}}, csl,
+      create<ast::BlockStatement>(ast::StatementList{})));
+
+  ast::CaseSelectorList default_csl;
+  auto* block_default = create<ast::BlockStatement>(ast::StatementList{});
+  switch_body.push_back(create<ast::CaseStatement>(default_csl, block_default));
+
+  auto* block = create<ast::BlockStatement>(ast::StatementList{
+      create<ast::VariableDeclStatement>(var),
+      create<ast::SwitchStatement>(Expr("a"), switch_body),
+  });
+  WrapInFunction(block);
+
+  EXPECT_FALSE(r()->Resolve());
+  EXPECT_EQ(r()->error(),
+            "12:34 error v-0026: the case selector values must have the same "
+            "type as the selector expression.");
+}
+
+TEST_F(ResolverControlBlockValidationTest,
+       NonUniqueCaseSelectorValueUint_Fail) {
+  // var a : u32 = 3;
+  // switch (a) {
+  //   case 0: {}
+  //   case 2, 2: {}
+  //   default: {}
+  // }
+  auto* var = Var("a", ty.u32(), ast::StorageClass::kNone, Expr(3u));
+
+  ast::CaseStatementList switch_body;
+  ast::CaseSelectorList csl_1;
+  csl_1.push_back(create<ast::UintLiteral>(ty.u32(), 0));
+  switch_body.push_back(create<ast::CaseStatement>(
+      csl_1, create<ast::BlockStatement>(ast::StatementList{})));
+
+  ast::CaseSelectorList csl_2;
+  csl_2.push_back(create<ast::UintLiteral>(ty.u32(), 2));
+  csl_2.push_back(create<ast::UintLiteral>(ty.u32(), 2));
+  switch_body.push_back(create<ast::CaseStatement>(
+      Source{Source::Location{12, 34}}, csl_2,
+      create<ast::BlockStatement>(ast::StatementList{})));
+
+  ast::CaseSelectorList default_csl;
+  auto* block_default = create<ast::BlockStatement>(ast::StatementList{});
+  switch_body.push_back(create<ast::CaseStatement>(default_csl, block_default));
+
+  auto* block = create<ast::BlockStatement>(ast::StatementList{
+      create<ast::VariableDeclStatement>(var),
+      create<ast::SwitchStatement>(Expr("a"), switch_body),
+  });
+  WrapInFunction(block);
+
+  EXPECT_FALSE(r()->Resolve());
+  EXPECT_EQ(
+      r()->error(),
+      "12:34 error v-0027: a literal value must not appear more than once "
+      "in the case selectors for a switch statement: '2'");
+}
+
+TEST_F(ResolverControlBlockValidationTest,
+       NonUniqueCaseSelectorValueSint_Fail) {
+  // var a : i32 = 2;
+  // switch (a) {
+  //   case 10: {}
+  //   case 0,1,2,10: {}
+  //   default: {}
+  // }
+  auto* var = Var("a", ty.i32(), ast::StorageClass::kNone, Expr(2));
+
+  ast::CaseStatementList switch_body;
+  ast::CaseSelectorList csl_1;
+  csl_1.push_back(Literal(10));
+  switch_body.push_back(create<ast::CaseStatement>(
+      csl_1, create<ast::BlockStatement>(ast::StatementList{})));
+
+  ast::CaseSelectorList csl_2;
+  csl_2.push_back(Literal(0));
+  csl_2.push_back(Literal(1));
+  csl_2.push_back(Literal(2));
+  csl_2.push_back(Literal(10));
+  switch_body.push_back(create<ast::CaseStatement>(
+      Source{Source::Location{12, 34}}, csl_2,
+      create<ast::BlockStatement>(ast::StatementList{})));
+
+  ast::CaseSelectorList default_csl;
+  auto* block_default = create<ast::BlockStatement>(ast::StatementList{});
+  switch_body.push_back(create<ast::CaseStatement>(default_csl, block_default));
+
+  auto* block = create<ast::BlockStatement>(ast::StatementList{
+      create<ast::VariableDeclStatement>(var),
+      create<ast::SwitchStatement>(Expr("a"), switch_body),
+  });
+  WrapInFunction(block);
+
+  EXPECT_FALSE(r()->Resolve());
+  EXPECT_EQ(
+      r()->error(),
+      "12:34 error v-0027: a literal value must not appear more than once in "
+      "the case selectors for a switch statement: '10'");
+}
+
+TEST_F(ResolverControlBlockValidationTest,
+       LastClauseLastStatementIsFallthrough_Fail) {
+  // var a : i32 = 2;
+  // switch (a) {
+  //   default: { fallthrough; }
+  // }
+  auto* var = Var("a", ty.i32(), ast::StorageClass::kNone, Expr(2));
+
+  ast::CaseSelectorList default_csl;
+  auto* block_default = create<ast::BlockStatement>(
+
+      ast::StatementList{
+          create<ast::FallthroughStatement>(Source{Source::Location{12, 34}}),
+      });
+  ast::CaseStatementList body;
+  body.push_back(create<ast::CaseStatement>(default_csl, block_default));
+
+  auto* block = create<ast::BlockStatement>(ast::StatementList{
+      create<ast::VariableDeclStatement>(var),
+      create<ast::SwitchStatement>(Expr("a"), body),
+  });
+  WrapInFunction(block);
+
+  EXPECT_FALSE(r()->Resolve());
+  EXPECT_EQ(
+      r()->error(),
+      "12:34 error v-0028: a fallthrough statement must not appear as the "
+      "last statement in last clause of a switch");
+}
+
+TEST_F(ResolverControlBlockValidationTest, SwitchCase_Pass) {
+  // var a : i32 = 2;
+  // switch (a) {
+  //   default: {}
+  //   case 5: {}
+  // }
+  auto* var = Var("a", ty.i32(), ast::StorageClass::kNone, Expr(2));
+
+  ast::CaseSelectorList default_csl;
+  auto* block_default = create<ast::BlockStatement>(ast::StatementList{});
+  ast::CaseStatementList body;
+  body.push_back(create<ast::CaseStatement>(Source{Source::Location{12, 34}},
+                                            default_csl, block_default));
+  ast::CaseSelectorList case_csl;
+  case_csl.push_back(Literal(5));
+  auto* block_case = create<ast::BlockStatement>(ast::StatementList{});
+  body.push_back(create<ast::CaseStatement>(case_csl, block_case));
+
+  auto* block = create<ast::BlockStatement>(ast::StatementList{
+      create<ast::VariableDeclStatement>(var),
+      create<ast::SwitchStatement>(Expr("a"), body),
+  });
+  WrapInFunction(block);
+
+  EXPECT_TRUE(r()->Resolve()) << r()->error();
+}
+
+TEST_F(ResolverControlBlockValidationTest, SwitchCaseAlias_Pass) {
+  // type MyInt = u32;
+  // var v: MyInt;
+  // switch(v){
+  //   default: {}
+  // }
+
+  auto* my_int = ty.alias("MyInt", ty.u32());
+  auto* var = Var("a", my_int, ast::StorageClass::kNone, Expr(2u));
+
+  ast::CaseSelectorList default_csl;
+  auto* block_default = create<ast::BlockStatement>(ast::StatementList{});
+  ast::CaseStatementList body;
+  body.push_back(create<ast::CaseStatement>(Source{Source::Location{12, 34}},
+                                            default_csl, block_default));
+
+  auto* block = create<ast::BlockStatement>(ast::StatementList{
+      create<ast::VariableDeclStatement>(var),
+      create<ast::SwitchStatement>(Expr("a"), body),
+  });
+  AST().AddConstructedType(my_int);
+
+  WrapInFunction(block);
+
+  EXPECT_TRUE(r()->Resolve()) << r()->error();
+}
+
+}  // namespace
+}  // namespace tint

src/resolver/resolver.cc

@@ -409,15 +409,7 @@ bool Resolver::Statement(ast::Statement* stmt) {
     return Return(r);
   }
   if (auto* s = stmt->As<ast::SwitchStatement>()) {
-    if (!Expression(s->condition())) {
-      return false;
-    }
-    for (auto* case_stmt : s->body()) {
-      if (!CaseStatement(case_stmt)) {
-        return false;
-      }
-    }
-    return true;
+    return Switch(s);
   }
   if (auto* v = stmt->As<ast::VariableDeclStatement>()) {
     return VariableDeclStatement(v);
@@ -1676,6 +1668,91 @@ bool Resolver::Return(ast::ReturnStatement* ret) {
   return result && ValidateReturn(ret);
 }
 
+bool Resolver::ValidateSwitch(const ast::SwitchStatement* s) {
+  auto* cond_type = TypeOf(s->condition())->UnwrapAll();
+  if (!cond_type->is_integer_scalar()) {
+    diagnostics_.add_error("v-0025",
+                           "switch statement selector expression must be of a "
+                           "scalar integer type",
+                           s->condition()->source());
+    return false;
+  }
+
+  bool has_default = false;
+  std::unordered_set<uint32_t> selector_set;
+
+  for (auto* case_stmt : s->body()) {
+    if (case_stmt->IsDefault()) {
+      if (has_default) {
+        // More than one default clause
+        diagnostics_.add_error(
+            "v-0008", "switch statement must have exactly one default clause",
+            case_stmt->source());
+        return false;
+      }
+      has_default = true;
+    }
+
+    for (auto* selector : case_stmt->selectors()) {
+      if (cond_type != selector->type()) {
+        diagnostics_.add_error("v-0026",
+                               "the case selector values must have the same "
+                               "type as the selector expression.",
+                               case_stmt->source());
+        return false;
+      }
+
+      auto v = selector->value_as_u32();
+      if (selector_set.find(v) != selector_set.end()) {
+        diagnostics_.add_error(
+            "v-0027",
+            "a literal value must not appear more than once in "
+            "the case selectors for a switch statement: '" +
+                builder_->str(selector) + "'",
+            case_stmt->source());
+        return false;
+      }
+      selector_set.emplace(v);
+    }
+  }
+
+  if (!has_default) {
+    // No default clause
+    diagnostics_.add_error("switch statement must have a default clause",
+                           s->source());
+    return false;
+  }
+
+  if (!s->body().empty()) {
+    auto* last_clause = s->body().back()->As<ast::CaseStatement>();
+    auto* last_stmt = last_clause->body()->last();
+    if (last_stmt && last_stmt->Is<ast::FallthroughStatement>()) {
+      diagnostics_.add_error("v-0028",
+                             "a fallthrough statement must not appear as "
+                             "the last statement in last clause of a switch",
+                             last_stmt->source());
+      return false;
+    }
+  }
+
+  return true;
+}
+
+bool Resolver::Switch(ast::SwitchStatement* s) {
+  if (!Expression(s->condition())) {
+    return false;
+  }
+  for (auto* case_stmt : s->body()) {
+    if (!CaseStatement(case_stmt)) {
+      return false;
+    }
+  }
+  if (!ValidateSwitch(s)) {
+    return false;
+  }
+  return true;
+}
+
 bool Resolver::ApplyStorageClassUsageToType(ast::StorageClass sc,
                                             type::Type* ty,
                                             Source usage) {

src/resolver/resolver.h

@@ -40,6 +40,7 @@ class Function;
 class IdentifierExpression;
 class MemberAccessorExpression;
 class ReturnStatement;
+class SwitchStatement;
 class UnaryOpExpression;
 class Variable;
 }  // namespace ast
@@ -220,6 +221,7 @@ class Resolver {
   bool UnaryOp(ast::UnaryOpExpression*);
   bool VariableDeclStatement(const ast::VariableDeclStatement*);
   bool Return(ast::ReturnStatement* ret);
+  bool Switch(ast::SwitchStatement* s);
 
   // AST and Type validation methods
   // Each return true on success, false on failure.
@@ -228,6 +230,7 @@ class Resolver {
   bool ValidateFunction(const ast::Function* func);
   bool ValidateStructure(const type::Struct* st);
   bool ValidateReturn(const ast::ReturnStatement* ret);
+  bool ValidateSwitch(const ast::SwitchStatement* s);
 
   /// @returns the semantic information for the array `arr`, building it if it
   /// hasn't been constructed already. If an error is raised, nullptr is

src/resolver/resolver_test.cc

@@ -248,14 +248,8 @@ TEST_F(ResolverTest, Stmt_Switch) {
   auto* lhs = Expr("v");
   auto* rhs = Expr(2.3f);
 
-  auto* body = Block(create<ast::AssignmentStatement>(lhs, rhs));
-  ast::CaseSelectorList lit;
-  lit.push_back(create<ast::SintLiteral>(ty.i32(), 3));
-
-  ast::CaseStatementList cases;
-  cases.push_back(create<ast::CaseStatement>(lit, body));
-
-  auto* stmt = create<ast::SwitchStatement>(Expr(2), cases);
+  auto* stmt =
+      Switch(Expr(2), Case(Literal(3), Block(Assign(lhs, rhs))), DefaultCase());
   WrapInFunction(v, stmt);
 
   EXPECT_TRUE(r()->Resolve()) << r()->error();

src/resolver/validation_test.cc

@@ -666,12 +666,10 @@ TEST_F(ResolverValidationTest, Stmt_BreakInLoop) {
 }
 
 TEST_F(ResolverValidationTest, Stmt_BreakInSwitch) {
-  WrapInFunction(Loop(Block(create<ast::SwitchStatement>(
-      Expr(1), ast::CaseStatementList{
-                   create<ast::CaseStatement>(
-                       ast::CaseSelectorList{Literal(1)},
-                       Block(create<ast::BreakStatement>(Source{{12, 34}}))),
-               }))));
+  WrapInFunction(Loop(Block(Switch(
+      Expr(1),
+      Case(Literal(1), Block(create<ast::BreakStatement>(Source{{12, 34}}))),
+      DefaultCase()))));
   EXPECT_TRUE(r()->Resolve()) << r()->error();
 }