Add diagnostic for function body followed by a `;`;. (#6122)

2 files changed, 21 insertions, 2 deletions

diff --git a/source/slang/slang-diagnostic-defs.h b/source/slang/slang-diagnostic-defs.h
index 7eddc16a9..915ed9b42 100644
--- a/source/slang/slang-diagnostic-defs.h
+++ b/source/slang/slang-diagnostic-defs.h
@@ -487,7 +487,11 @@ DIAGNOSTIC(
     Warning,
     unintendedEmptyStatement,
     "potentially unintended empty statement at this location; use {} instead.")
-
+DIAGNOSTIC(
+    20102,
+    Error,
+    unexpectedBodyAfterSemicolon,
+    "unexpected function body after signature declaration, is this ';' a typo?")
 DIAGNOSTIC(30102, Error, declNotAllowed, "$0 is not allowed here.")
 
 // 29xxx - Snippet parsing and inline asm
diff --git a/source/slang/slang-parser.cpp b/source/slang/slang-parser.cpp
index 98cfd121c..81619b700 100644
--- a/source/slang/slang-parser.cpp
+++ b/source/slang/slang-parser.cpp
@@ -1802,9 +1802,17 @@ public:
 /// Parse an optional body statement for a declaration that can have a body.
 static Stmt* parseOptBody(Parser* parser)
 {
-    if (AdvanceIf(parser, TokenType::Semicolon))
+    Token semiColonToken;
+    if (AdvanceIf(parser, TokenType::Semicolon, &semiColonToken))
     {
         // empty body
+        // if we see a `{` after a `;`, it is very likely an user error to
+        // have the `;`, so we will provide a better diagnostic for it.
+        if (peekTokenType(parser) == TokenType::LBrace)
+        {
+            parser->sink->diagnose(semiColonToken.loc, Diagnostics::unexpectedBodyAfterSemicolon);
+            return parser->parseBlockStatement();
+        }
         return nullptr;
     }
     else
@@ -4841,6 +4849,13 @@ static DeclBase* ParseDeclWithModifiers(
             // We shouldn't be seeing an LBrace or an LParent when expecting a decl.
             // However recovery logic may lead us here. In this case we just
             // skip the whole `{}` block and return an empty decl.
+            if (!parser->isRecovering)
+            {
+                parser->sink->diagnose(
+                    loc,
+                    Diagnostics::unexpectedToken,
+                    parser->tokenReader.peekToken());
+            }
             SkipBalancedToken(&parser->tokenReader);
             decl = parser->astBuilder->create<EmptyDecl>();
             decl->loc = loc;