SkSL: Ensure struct declarations contain at least one member

Bug: skia:11314
Change-Id: I66476543462ae378a5bfb6cbd902dfa2f5fc45f5
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/369917
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>

gn/sksl_tests.gni

@@ -96,6 +96,7 @@ sksl_error_tests = [
   "/sksl/errors/DuplicateFunction.sksl",
   "/sksl/errors/DuplicateOutput.sksl",
   "/sksl/errors/DuplicateSymbol.sksl",
+  "/sksl/errors/EmptyStruct.sksl",
   "/sksl/errors/EnumValueMustBeConstInt.sksl",
   "/sksl/errors/ErrorsInDeadCode.sksl",
   "/sksl/errors/FloatRemainder.sksl",

resources/sksl/errors/BinaryInvalidType.sksl

@@ -11,6 +11,7 @@ void functionBoth() {
 }
 
 struct S {
+    float x;
 } s;
 
 void structLeft() {

resources/sksl/errors/EmptyStruct.sksl

@@ -0,0 +1 @@
+struct S { };

resources/sksl/errors/InvalidUnary.sksl

@@ -1,4 +1,4 @@
-struct Foo {} bar;
+struct Foo { float x; } bar;
 
 void preincrement_matrix()  { float4x4 x = float4x4(1); ++x; }
 void predecrement_vector()  { float3 x = float3(1); --x; }

src/sksl/SkSLParser.cpp

@@ -626,6 +626,11 @@ ASTNode::ID Parser::structDeclaration() {
     if (!this->expect(Token::Kind::TK_RBRACE, "'}'")) {
         return ASTNode::ID::Invalid();
     }
+    if (fields.empty()) {
+        this->error(name.fOffset,
+                    "struct '" + this->text(name) + "' must contain at least one field");
+        return ASTNode::ID::Invalid();
+    }
     std::unique_ptr<Type> newType = Type::MakeStructType(name.fOffset, this->text(name), fields);
     if (struct_is_too_deeply_nested(*newType, kMaxStructDepth)) {
         this->error(name.fOffset, "struct '" + this->text(name) + "' is too deeply nested");

tests/sksl/errors/BinaryInvalidType.glsl

@@ -3,13 +3,13 @@
 error: 2: type mismatch: '*' cannot operate on '<INVALID>', 'int'
 error: 6: type mismatch: '*' cannot operate on 'int', '<INVALID>'
 error: 10: type mismatch: '*' cannot operate on '<INVALID>', '<INVALID>'
-error: 17: type mismatch: '*' cannot operate on 'S', 'int'
-error: 21: type mismatch: '*' cannot operate on 'int', 'S'
-error: 25: type mismatch: '*' cannot operate on 'S', 'S'
-error: 31: type mismatch: '*' cannot operate on 'sampler2D', 'int'
-error: 35: type mismatch: '*' cannot operate on 'int', 'sampler2D'
-error: 39: type mismatch: '*' cannot operate on 'sampler2D', 'sampler2D'
-error: 45: type mismatch: '*' cannot operate on 'int[1]', 'int'
-error: 49: type mismatch: '*' cannot operate on 'int', 'int[1]'
-error: 53: type mismatch: '*' cannot operate on 'int[1]', 'int[1]'
+error: 18: type mismatch: '*' cannot operate on 'S', 'int'
+error: 22: type mismatch: '*' cannot operate on 'int', 'S'
+error: 26: type mismatch: '*' cannot operate on 'S', 'S'
+error: 32: type mismatch: '*' cannot operate on 'sampler2D', 'int'
+error: 36: type mismatch: '*' cannot operate on 'int', 'sampler2D'
+error: 40: type mismatch: '*' cannot operate on 'sampler2D', 'sampler2D'
+error: 46: type mismatch: '*' cannot operate on 'int[1]', 'int'
+error: 50: type mismatch: '*' cannot operate on 'int', 'int[1]'
+error: 54: type mismatch: '*' cannot operate on 'int[1]', 'int[1]'
 12 errors

tests/sksl/errors/EmptyStruct.glsl

@@ -0,0 +1,4 @@
+### Compilation failed:
+
+error: 1: struct 'S' must contain at least one field
+1 error