[mlir-lsp-server] Add support for hover on symbol references

[rriddle]

Summary

For now the hover simply shows the same information as hovering on the operation
name. If necessary this can be tweaked to something symbol specific later.

Depends On D103727

[jpienaar]

mlir/test/mlir-lsp-server/hover.test

145

Why does this add at 4? For the symbol ref we just highlight func?

[rriddle]

mlir/test/mlir-lsp-server/hover.test

145

Oops, thanks for the catch.

mlir/lib/Tools/mlir-lsp-server/MLIRServer.cpp

Optional<lsp::Hover> MLIRDocument::findHover(const lsp::URIForFile &uri,
   llvm::SMRange hoverRange;
 
   // Check for Hovers on operations and results.
   for (const AsmParserState::OperationDefinition &op : asmState.getOpDefs()) {
     // Check if the position points at this operation.
     if (contains(op.loc, posLoc))
       return buildHoverForOperation(op);
 
+    // Check if the position points at the symbol name.
+    for (auto &use : op.symbolUses)
+      if (contains(use, posLoc))
+        return buildHoverForOperation(op);
+
     // Check if the position points at a result group.
     for (unsigned i = 0, e = op.resultGroups.size(); i < e; ++i) {
       const auto &result = op.resultGroups[i];
       if (!isDefOrUse(result.second, posLoc, &hoverRange))
         continue;
 
       // Get the range of results covered by the over position.
       unsigned resultStart = result.first;

mlir/test/mlir-lsp-server/hover.test

 // CHECK-NEXT:      },
 // CHECK-NEXT:      "start": {
 // CHECK-NEXT:        "character": 0,
 // CHECK-NEXT:        "line": 0
 // CHECK-NEXT:      }
 // CHECK-NEXT:    }
 // CHECK-NEXT:  }
 // -----
-{"jsonrpc":"2.0","id":6,"method":"shutdown"}
+// Hover on a symbol reference.
+{"jsonrpc":"2.0","id":6,"method":"textDocument/hover","params":{
+  "textDocument":{"uri":"test:///foo.mlir"},
+  "position":{"line":0,"character":8}
+}}
+//      CHECK:  "id": 6,
+// CHECK-NEXT:  "jsonrpc": "2.0",
+// CHECK-NEXT:  "result": {
+// CHECK-NEXT:    "contents": {
+// CHECK-NEXT:      "kind": "markdown",
+// CHECK-NEXT:      "value": "\"func\" : public @foo\n\nGeneric Form:\n\n```mlir\n\"func\"() ( {\n}) {sym_name = \"foo\", type = (i1) -> ()} : () -> ()\n```\n"
+// CHECK-NEXT:    },
+// CHECK-NEXT:    "range": {
+// CHECK-NEXT:      "end": {
+// CHECK-NEXT:        "character": 4,
+// CHECK-NEXT:        "line": 0
+// CHECK-NEXT:      },
+// CHECK-NEXT:      "start": {
+// CHECK-NEXT:        "character": 0,
+// CHECK-NEXT:        "line": 0
+// CHECK-NEXT:      }
+// CHECK-NEXT:    }
+// CHECK-NEXT:  }
+// -----
+{"jsonrpc":"2.0","id":7,"method":"shutdown"}
 // -----
 {"jsonrpc":"2.0","method":"exit"}