Fix compiles on VS2017 and GCC

VS2017 took issue with treating size_t and uint32_t the same. It also
couldn't find various alphanumeric is* functions without the <cctype>
header. Gcc complainted about a variable potentially used uninitialized.

Change-Id: I452b68c6597bae254f32e5a350656e65c8934b6e
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/18901
Reviewed-by: dan sinclair <dsinclair@google.com>

src/ast/import.cc

@@ -14,6 +14,8 @@
 
 #include "src/ast/import.h"
 
+#include <cctype>
+
 namespace tint {
 namespace ast {
 

src/reader/wgsl/lexer.cc

@@ -18,6 +18,7 @@
 #include <errno.h>
 #include <stdlib.h>
 
+#include <cctype>
 #include <limits>
 
 namespace tint {

src/reader/wgsl/parser_impl.cc

@@ -808,7 +808,7 @@ ast::type::Type* ParserImpl::type_decl_pointer(Token t) {
 ast::type::Type* ParserImpl::type_decl_vector(Token t) {
   next();  // Consume the peek
 
-  size_t count = 2;
+  uint32_t count = 2;
   if (t.IsVec3())
     count = 3;
   else if (t.IsVec4())
@@ -856,7 +856,7 @@ ast::type::Type* ParserImpl::type_decl_array(Token t) {
   }
 
   t = next();
-  size_t size = 0;
+  uint32_t size = 0;
   if (t.IsComma()) {
     t = next();
     if (!t.IsIntLiteral()) {
@@ -867,7 +867,7 @@ ast::type::Type* ParserImpl::type_decl_array(Token t) {
       set_error(t, "invalid size for array declaration");
       return nullptr;
     }
-    size = static_cast<size_t>(t.to_i32());
+    size = static_cast<uint32_t>(t.to_i32());
     t = next();
   }
   if (!t.IsGreaterThan()) {
@@ -882,8 +882,8 @@ ast::type::Type* ParserImpl::type_decl_array(Token t) {
 ast::type::Type* ParserImpl::type_decl_matrix(Token t) {
   next();  // Consume the peek
 
-  size_t rows = 2;
-  size_t columns = 2;
+  uint32_t rows = 2;
+  uint32_t columns = 2;
   if (t.IsMat3x2() || t.IsMat3x3() || t.IsMat3x4()) {
     rows = 3;
   } else if (t.IsMat4x2() || t.IsMat4x3() || t.IsMat4x4()) {
@@ -1181,8 +1181,7 @@ ParserImpl::struct_member_decoration() {
     return nullptr;
   }
 
-  return std::make_unique<ast::StructMemberOffsetDecoration>(
-      static_cast<size_t>(val));
+  return std::make_unique<ast::StructMemberOffsetDecoration>(val);
 }
 
 // function_decl

src/scope_stack_test.cc

@@ -37,7 +37,7 @@ TEST_F(ScopeStackTest, Global_SetWithPointer) {
   ScopeStack<ast::Variable*> s;
   s.set_global("var", &v);
 
-  ast::Variable* v2;
+  ast::Variable* v2 = nullptr;
   EXPECT_TRUE(s.get("var", &v2));
   EXPECT_EQ(v2->name(), "my_var");
 }