tint: Add new methods to semantic Switch nodes

• Add sem::SwitchStatement::Cases()
• Add sem::CaseStatement::Selectors()
• Add ast::SwitchStatement -> sem::SwitchStatement mapping

Removes a bunch of hopping between the AST and SEM to get at this data.

Change-Id: If48d78e7a386aa0b34c6d00ad9af1d53cb236f12
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/91024
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: Dan Sinclair <dsinclair@chromium.org>

src/tint/resolver/resolver.cc

@@ -870,10 +870,13 @@ sem::CaseStatement* Resolver::CaseStatement(const ast::CaseStatement* stmt) {
     auto* sem =
         builder_->create<sem::CaseStatement>(stmt, current_compound_statement_, current_function_);
     return StatementScope(stmt, sem, [&] {
+        sem->Selectors().reserve(stmt->selectors.size());
         for (auto* sel : stmt->selectors) {
-            if (!Expression(sel)) {
+            auto* expr = Expression(sel);
+            if (!expr) {
                 return false;
             }
+            sem->Selectors().emplace_back(expr);
         }
         Mark(stmt->body);
         auto* body = BlockStatement(stmt->body);
@@ -2140,6 +2143,7 @@ sem::SwitchStatement* Resolver::SwitchStatement(const ast::SwitchStatement* stmt
                 return false;
             }
             behaviors.Add(c->Behaviors());
+            sem->Cases().emplace_back(c);
         }
 
         if (behaviors.Contains(sem::Behavior::kBreak)) {

src/tint/resolver/resolver_behavior_test.cc

@@ -19,6 +19,7 @@
 #include "src/tint/sem/expression.h"
 #include "src/tint/sem/for_loop_statement.h"
 #include "src/tint/sem/if_statement.h"
+#include "src/tint/sem/switch_statement.h"
 
 using namespace tint::number_suffixes;  // NOLINT
 

src/tint/resolver/resolver_test.cc

@@ -42,6 +42,7 @@
 #include "src/tint/sem/reference.h"
 #include "src/tint/sem/sampled_texture.h"
 #include "src/tint/sem/statement.h"
+#include "src/tint/sem/switch_statement.h"
 #include "src/tint/sem/variable.h"
 
 using ::testing::ElementsAre;
@@ -111,11 +112,11 @@ TEST_F(ResolverTest, Stmt_Case) {
 
     auto* assign = Assign(lhs, rhs);
     auto* block = Block(assign);
-    ast::CaseSelectorList lit;
-    lit.push_back(Expr(3_i));
-    auto* cse = create<ast::CaseStatement>(lit, block);
+    auto* sel = Expr(3_i);
+    auto* cse = Case(sel, block);
+    auto* def = DefaultCase();
     auto* cond_var = Var("c", ty.i32());
-    auto* sw = Switch(cond_var, cse, DefaultCase());
+    auto* sw = Switch(cond_var, cse, def);
     WrapInFunction(v, cond_var, sw);
 
     EXPECT_TRUE(r()->Resolve()) << r()->error();
@@ -127,6 +128,13 @@ TEST_F(ResolverTest, Stmt_Case) {
     EXPECT_EQ(StmtOf(lhs), assign);
     EXPECT_EQ(StmtOf(rhs), assign);
     EXPECT_EQ(BlockOf(assign), block);
+    auto* sem = Sem().Get(sw);
+    ASSERT_EQ(sem->Cases().size(), 2u);
+    EXPECT_EQ(sem->Cases()[0]->Declaration(), cse);
+    ASSERT_EQ(sem->Cases()[0]->Selectors().size(), 1u);
+    EXPECT_EQ(sem->Cases()[0]->Selectors()[0]->Declaration(), sel);
+    EXPECT_EQ(sem->Cases()[1]->Declaration(), def);
+    EXPECT_EQ(sem->Cases()[1]->Selectors().size(), 0u);
 }
 
 TEST_F(ResolverTest, Stmt_Block) {

src/tint/sem/switch_statement.h

@@ -15,6 +15,8 @@
 #ifndef SRC_TINT_SEM_SWITCH_STATEMENT_H_
 #define SRC_TINT_SEM_SWITCH_STATEMENT_H_
 
+#include <vector>
+
 #include "src/tint/sem/block_statement.h"
 
 // Forward declarations
@@ -22,6 +24,10 @@ namespace tint::ast {
 class CaseStatement;
 class SwitchStatement;
 }  // namespace tint::ast
+namespace tint::sem {
+class CaseStatement;
+class Expression;
+}  // namespace tint::sem
 
 namespace tint::sem {
 
@@ -41,6 +47,15 @@ class SwitchStatement final : public Castable<SwitchStatement, CompoundStatement
 
     /// @return the AST node for this statement
     const ast::SwitchStatement* Declaration() const;
+
+    /// @returns the case statements for this switch
+    std::vector<const CaseStatement*>& Cases() { return cases_; }
+
+    /// @returns the case statements for this switch
+    const std::vector<const CaseStatement*>& Cases() const { return cases_; }
+
+  private:
+    std::vector<const CaseStatement*> cases_;
 };
 
 /// Holds semantic information about a switch case statement
@@ -66,8 +81,15 @@ class CaseStatement final : public Castable<CaseStatement, CompoundStatement> {
     /// @returns the case body block statement
     const BlockStatement* Body() const { return body_; }
 
+    /// @returns the selectors for the case
+    std::vector<const Expression*>& Selectors() { return selectors_; }
+
+    /// @returns the selectors for the case
+    const std::vector<const Expression*>& Selectors() const { return selectors_; }
+
   private:
     const BlockStatement* body_ = nullptr;
+    std::vector<const Expression*> selectors_;
 };
 
 }  // namespace tint::sem

src/tint/sem/type_mappings.h

@@ -30,6 +30,7 @@ class Node;
 class Statement;
 class Struct;
 class StructMember;
+class SwitchStatement;
 class Type;
 class TypeDecl;
 class Variable;
@@ -46,6 +47,7 @@ class Node;
 class Statement;
 class Struct;
 class StructMember;
+class SwitchStatement;
 class Type;
 class Variable;
 }  // namespace tint::sem
@@ -68,6 +70,7 @@ struct TypeMappings {
     Statement* operator()(ast::Statement*);
     Struct* operator()(ast::Struct*);
     StructMember* operator()(ast::StructMember*);
+    SwitchStatement* operator()(ast::SwitchStatement*);
     Type* operator()(ast::Type*);
     Type* operator()(ast::TypeDecl*);
     Variable* operator()(ast::Variable*);