[mlir][flang] Do not prevent integer types from being parsed as MLIR keywords

DialectAsmParser::parseKeyword is rejecting `'i' digit+` while it is
a valid identifier according to mlir/docs/LangRef.md.

Integer types actually used to be TOK_KEYWORD a while back before the
change: 6af866c58d.

This patch Modifies `isCurrentTokenAKeyword` to return true for tokens that
match integer types too.

The motivation for this change is the parsing of `!fir.type<{` `component-name: component-type,`+ `}>`
type in FIR that represent Fortran derived types. The component-names are
parsed as keywords, and can very well be i32 or any ixxx (which are
valid Fortran derived type component names).

The Quant dialect type parser had to be modified since it relied on `iw` not
being parsed as keywords.

Differential Revision: https://reviews.llvm.org/D108913

flang/test/Fir/fir-types.fir

@@ -25,12 +25,14 @@ func private @it7() -> !fir.char<4,?>
 // CHECK-LABEL: func private @dvd4() -> !fir.type<derived4(p:i8){f:f32}>
 // CHECK-LABEL: func private @dvd5() -> !fir.type<derived5(p1:i8,p2:i8,p3:i8,p4:i8,p5:i8){f1:f32,f2:f32,f3:f32,f4:f32,f5:f32,f6:f32,f7:f32,f8:f32}>
 // CHECK-LABEL: func private @dvd6() -> !fir.type<derived6{f:!fir.ptr<!fir.type<derived6>>}>
+// CHECK-LABEL: func private @dvd7() -> !fir.type<derived_with_field_name_same_as_integer_type{i32:f32}>
 func private @dvd1() -> !fir.type<derived1>
 func private @dvd2() -> !fir.type<derived2(p:i32)>
 func private @dvd3() -> !fir.type<derived3{f:f32}>
 func private @dvd4() -> !fir.type<derived4(p:i8){f:f32}>
 func private @dvd5() -> !fir.type<derived5(p1:i8,p2:i8,p3:i8,p4:i8,p5:i8){f1:f32,f2:f32,f3:f32,f4:f32,f5:f32,f6:f32,f7:f32,f8:f32}>
 func private @dvd6() -> !fir.type<derived6{f:!fir.ptr<!fir.type<derived6>>}>
+func private @dvd7() -> !fir.type<derived_with_field_name_same_as_integer_type{i32:f32}>
 
 // FIR array types
 // CHECK-LABEL: func private @arr1() -> !fir.array<10xf32>

mlir/lib/Dialect/Quant/IR/TypeParser.cpp

@@ -29,15 +29,16 @@ static IntegerType parseStorageType(DialectAsmParser &parser, bool &isSigned) {
   // Parse storage type (alpha_ident, integer_literal).
   StringRef identifier;
   unsigned storageTypeWidth = 0;
-  if (failed(parser.parseOptionalKeyword(&identifier))) {
-    // If we didn't parse a keyword, this must be a signed type.
-    if (parser.parseType(type))
+  OptionalParseResult result = parser.parseOptionalType(type);
+  if (result.hasValue()) {
+    if (!succeeded(*result)) {
+      parser.parseType(type);
       return nullptr;
-    isSigned = true;
+    }
+    isSigned = !type.isUnsigned();
     storageTypeWidth = type.getWidth();
-
+  } else if (succeeded(parser.parseKeyword(&identifier))) {
     // Otherwise, this must be an unsigned integer (`u` integer-literal).
-  } else {
     if (!identifier.consume_front("u")) {
       parser.emitError(typeLoc, "illegal storage type prefix");
       return nullptr;
@@ -48,6 +49,8 @@ static IntegerType parseStorageType(DialectAsmParser &parser, bool &isSigned) {
     }
     isSigned = false;
     type = parser.getBuilder().getIntegerType(storageTypeWidth);
+  } else {
+    return nullptr;
   }
 
   if (storageTypeWidth == 0 ||

mlir/lib/Parser/DialectSymbolParser.cpp

@@ -250,7 +250,7 @@ public:
 
   /// Returns true if the current token corresponds to a keyword.
   bool isCurrentTokenAKeyword() const {
-    return parser.getToken().is(Token::bare_identifier) ||
+    return parser.getToken().isAny(Token::bare_identifier, Token::inttype) ||
            parser.getToken().isKeyword();
   }
 

mlir/test/mlir-tblgen/types.mlir

@@ -504,3 +504,27 @@ func @elements_attr_not_index() {
   "test.indexElementsAttr"() {attr = dense<[1, 2]>:tensor<2xi32>} : () -> ()
   return
 }
+
+// -----
+
+// CHECK-LABEL: @struct_success
+func @struct_success() {
+  "test.simple_struct"() : () -> (!test.struct<{a, i32}, {b, f64}>)
+  return
+}
+
+// -----
+
+// CHECK-LABEL: @struct_with_field_names_like_types
+func @struct_with_field_names_like_types() {
+  "test.struct_with_field_names_like_types"() : () -> (!test.struct<{i32, i32}, {f64, f64}>)
+  return
+}
+
+// -----
+
+func @struct_bad_keywords() {
+  // expected-error@+1 {{expected valid keyword}}
+  "test.struct_bad_keywords"() : () -> (!test.struct<{42, i32}>)
+  return
+}